DEFINITION ty3_nf2_inv_abst()
TYPE =
       g:G
         .c:C
           .t:T
             .w:T
               .u:T
                 .ty3 g c t (THead (Bind Abst) w u)
                   (nf2 c t
                        (nf2 c w
                             (ty3_nf2_inv_abst_premise c w u
                                  (ex4_2
                                       T
                                       T
                                       λv:T.λ:T.eq T t (THead (Bind Abst) w v)
                                       λ:T.λw0:T.ty3 g c w w0
                                       λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                       λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v))))
BODY =
        assume gG
        assume cC
        assume tT
        assume wT
        assume uT
        suppose Hty3 g c t (THead (Bind Abst) w u)
        suppose H0nf2 c t
        suppose H1nf2 c w
        suppose H2ty3_nf2_inv_abst_premise c w u
          (H_x
             by (ty3_nf2_inv_all . . . . H H0)

                or3
                  ex3_2
                    T
                    T
                    λw:T.λu0:T.eq T t (THead (Bind Abst) w u0)
                    λw:T.λ:T.nf2 c w
                    λw:T.λu0:T.nf2 (CHead c (Bind Abst) w) u0
                  ex nat λn:nat.eq T t (TSort n)
                  ex3_2
                    TList
                    nat
                    λws:TList.λi:nat.eq T t (THeads (Flat Appl) ws (TLRef i))
                    λws:TList.λ:nat.nfs2 c ws
                    λ:TList.λi:nat.nf2 c (TLRef i)
          end of H_x
          (H3consider H_x
          we proceed by induction on H3 to prove 
             ex4_2
               T
               T
               λv:T.λ:T.eq T t (THead (Bind Abst) w v)
               λ:T.λw0:T.ty3 g c w w0
               λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
               λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
             case or3_intro0 : H4:ex3_2 T T λw0:T.λu0:T.eq T t (THead (Bind Abst) w0 u0) λw0:T.λ:T.nf2 c w0 λw0:T.λu0:T.nf2 (CHead c (Bind Abst) w0) u0 
                the thesis becomes 
                ex4_2
                  T
                  T
                  λv:T.λ:T.eq T t (THead (Bind Abst) w v)
                  λ:T.λw0:T.ty3 g c w w0
                  λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                  λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                   we proceed by induction on H4 to prove 
                      ex4_2
                        T
                        T
                        λv:T.λ:T.eq T t (THead (Bind Abst) w v)
                        λ:T.λw0:T.ty3 g c w w0
                        λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                        λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                      case ex3_2_intro : x0:T x1:T H5:eq T t (THead (Bind Abst) x0 x1) H6:nf2 c x0 H7:nf2 (CHead c (Bind Abst) x0) x1 
                         the thesis becomes 
                         ex4_2
                           T
                           T
                           λv:T.λ:T.eq T t (THead (Bind Abst) w v)
                           λ:T.λw0:T.ty3 g c w w0
                           λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                           λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                            (H8
                               we proceed by induction on H5 to prove ty3 g c (THead (Bind Abst) x0 x1) (THead (Bind Abst) w u)
                                  case refl_equal : 
                                     the thesis becomes the hypothesis H
ty3 g c (THead (Bind Abst) x0 x1) (THead (Bind Abst) w u)
                            end of H8
                            by (ty3_correct . . . . H8)
                            we proved ex T λt:T.ty3 g c (THead (Bind Abst) w u) t
                            we proceed by induction on the previous result to prove 
                               ex4_2
                                 T
                                 T
                                 λv:T.λ:T.eq T (THead (Bind Abst) x0 x1) (THead (Bind Abst) w v)
                                 λ:T.λw0:T.ty3 g c w w0
                                 λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                 λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                               case ex_intro : x:T H9:ty3 g c (THead (Bind Abst) w u) x 
                                  the thesis becomes 
                                  ex4_2
                                    T
                                    T
                                    λv:T.λ:T.eq T (THead (Bind Abst) x0 x1) (THead (Bind Abst) w v)
                                    λ:T.λw0:T.ty3 g c w w0
                                    λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                    λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                                     by (ty3_gen_bind . . . . . . H9)
                                     we proved 
                                        ex3_2
                                          T
                                          T
                                          λt2:T.λ:T.pc3 c (THead (Bind Abst) w t2) x
                                          λ:T.λt:T.ty3 g c w t
                                          λt2:T.λ:T.ty3 g (CHead c (Bind Abst) w) u t2
                                     we proceed by induction on the previous result to prove 
                                        ex4_2
                                          T
                                          T
                                          λv:T.λ:T.eq T (THead (Bind Abst) x0 x1) (THead (Bind Abst) w v)
                                          λ:T.λw0:T.ty3 g c w w0
                                          λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                          λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                                        case ex3_2_intro : x2:T x3:T :pc3 c (THead (Bind Abst) w x2) x H11:ty3 g c w x3 H12:ty3 g (CHead c (Bind Abst) w) u x2 
                                           the thesis becomes 
                                           ex4_2
                                             T
                                             T
                                             λv:T.λ:T.eq T (THead (Bind Abst) x0 x1) (THead (Bind Abst) w v)
                                             λ:T.λw0:T.ty3 g c w w0
                                             λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                             λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                                              by (ty3_gen_bind . . . . . . H8)
                                              we proved 
                                                 ex3_2
                                                   T
                                                   T
                                                   λt2:T.λ:T.pc3 c (THead (Bind Abst) x0 t2) (THead (Bind Abst) w u)
                                                   λ:T.λt:T.ty3 g c x0 t
                                                   λt2:T.λ:T.ty3 g (CHead c (Bind Abst) x0) x1 t2
                                              we proceed by induction on the previous result to prove 
                                                 ex4_2
                                                   T
                                                   T
                                                   λv:T.λ:T.eq T (THead (Bind Abst) x0 x1) (THead (Bind Abst) w v)
                                                   λ:T.λw0:T.ty3 g c w w0
                                                   λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                                   λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                                                 case ex3_2_intro : x4:T x5:T H13:pc3 c (THead (Bind Abst) x0 x4) (THead (Bind Abst) w u) :ty3 g c x0 x5 H15:ty3 g (CHead c (Bind Abst) x0) x1 x4 
                                                    the thesis becomes 
                                                    ex4_2
                                                      T
                                                      T
                                                      λv:T.λ:T.eq T (THead (Bind Abst) x0 x1) (THead (Bind Abst) w v)
                                                      λ:T.λw0:T.ty3 g c w w0
                                                      λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                                      λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                                                       by (pc3_gen_abst . . . . . H13)
                                                       we proved land (pc3 c x0 w) b:B.u:T.(pc3 (CHead c (Bind b) u) x4 u)
                                                       we proceed by induction on the previous result to prove 
                                                          ex4_2
                                                            T
                                                            T
                                                            λv:T.λ:T.eq T (THead (Bind Abst) x0 x1) (THead (Bind Abst) w v)
                                                            λ:T.λw0:T.ty3 g c w w0
                                                            λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                                            λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                                                          case conj : H16:pc3 c x0 w H17:b:B.u0:T.(pc3 (CHead c (Bind b) u0) x4 u) 
                                                             the thesis becomes 
                                                             ex4_2
                                                               T
                                                               T
                                                               λv:T.λ:T.eq T (THead (Bind Abst) x0 x1) (THead (Bind Abst) w v)
                                                               λ:T.λw0:T.ty3 g c w w0
                                                               λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                                               λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                                                                (H_yby (pc3_nf2 . . . H16 H6 H1) we proved eq T x0 w
                                                                (H18
                                                                   we proceed by induction on H_y to prove ty3 g (CHead c (Bind Abst) w) x1 x4
                                                                      case refl_equal : 
                                                                         the thesis becomes the hypothesis H15
ty3 g (CHead c (Bind Abst) w) x1 x4
                                                                end of H18
                                                                (H19
                                                                   we proceed by induction on H_y to prove nf2 (CHead c (Bind Abst) w) x1
                                                                      case refl_equal : 
                                                                         the thesis becomes the hypothesis H7
nf2 (CHead c (Bind Abst) w) x1
                                                                end of H19
                                                                (h1
                                                                   by (refl_equal . .)
eq T (THead (Bind Abst) w x1) (THead (Bind Abst) w x1)
                                                                end of h1
                                                                (h2
                                                                   by (H17 . .)
                                                                   we proved pc3 (CHead c (Bind Abst) w) x4 u
                                                                   by (ty3_conv . . . . H12 . . H18 previous)
ty3 g (CHead c (Bind Abst) w) x1 u
                                                                end of h2
                                                                by (ex4_2_intro . . . . . . . . h1 H11 h2 H19)
                                                                we proved 
                                                                   ex4_2
                                                                     T
                                                                     T
                                                                     λv:T.λ:T.eq T (THead (Bind Abst) w x1) (THead (Bind Abst) w v)
                                                                     λ:T.λw0:T.ty3 g c w w0
                                                                     λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                                                     λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                                                                by (eq_ind_r . . . previous . H_y)

                                                                   ex4_2
                                                                     T
                                                                     T
                                                                     λv:T.λ:T.eq T (THead (Bind Abst) x0 x1) (THead (Bind Abst) w v)
                                                                     λ:T.λw0:T.ty3 g c w w0
                                                                     λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                                                     λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v

                                                          ex4_2
                                                            T
                                                            T
                                                            λv:T.λ:T.eq T (THead (Bind Abst) x0 x1) (THead (Bind Abst) w v)
                                                            λ:T.λw0:T.ty3 g c w w0
                                                            λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                                            λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v

                                                 ex4_2
                                                   T
                                                   T
                                                   λv:T.λ:T.eq T (THead (Bind Abst) x0 x1) (THead (Bind Abst) w v)
                                                   λ:T.λw0:T.ty3 g c w w0
                                                   λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                                   λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v

                                        ex4_2
                                          T
                                          T
                                          λv:T.λ:T.eq T (THead (Bind Abst) x0 x1) (THead (Bind Abst) w v)
                                          λ:T.λw0:T.ty3 g c w w0
                                          λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                          λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                            we proved 
                               ex4_2
                                 T
                                 T
                                 λv:T.λ:T.eq T (THead (Bind Abst) x0 x1) (THead (Bind Abst) w v)
                                 λ:T.λw0:T.ty3 g c w w0
                                 λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                 λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                            by (eq_ind_r . . . previous . H5)

                               ex4_2
                                 T
                                 T
                                 λv:T.λ:T.eq T t (THead (Bind Abst) w v)
                                 λ:T.λw0:T.ty3 g c w w0
                                 λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                 λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v

                      ex4_2
                        T
                        T
                        λv:T.λ:T.eq T t (THead (Bind Abst) w v)
                        λ:T.λw0:T.ty3 g c w w0
                        λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                        λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
             case or3_intro1 : H4:ex nat λn:nat.eq T t (TSort n) 
                the thesis becomes 
                ex4_2
                  T
                  T
                  λv:T.λ:T.eq T t (THead (Bind Abst) w v)
                  λ:T.λw0:T.ty3 g c w w0
                  λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                  λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                   we proceed by induction on H4 to prove 
                      ex4_2
                        T
                        T
                        λv:T.λ:T.eq T t (THead (Bind Abst) w v)
                        λ:T.λw0:T.ty3 g c w w0
                        λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                        λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                      case ex_intro : x:nat H5:eq T t (TSort x) 
                         the thesis becomes 
                         ex4_2
                           T
                           T
                           λv:T.λ:T.eq T t (THead (Bind Abst) w v)
                           λ:T.λw0:T.ty3 g c w w0
                           λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                           λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                            (H6
                               we proceed by induction on H5 to prove ty3 g c (TSort x) (THead (Bind Abst) w u)
                                  case refl_equal : 
                                     the thesis becomes the hypothesis H
ty3 g c (TSort x) (THead (Bind Abst) w u)
                            end of H6
                            by (ty3_gen_sort . . . . H6)
                            we proved pc3 c (TSort (next g x)) (THead (Bind Abst) w u)
                            by (pc3_gen_sort_abst . . . . previous .)
                            we proved 
                               ex4_2
                                 T
                                 T
                                 λv:T.λ:T.eq T (TSort x) (THead (Bind Abst) w v)
                                 λ:T.λw0:T.ty3 g c w w0
                                 λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                 λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                            by (eq_ind_r . . . previous . H5)

                               ex4_2
                                 T
                                 T
                                 λv:T.λ:T.eq T t (THead (Bind Abst) w v)
                                 λ:T.λw0:T.ty3 g c w w0
                                 λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                 λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v

                      ex4_2
                        T
                        T
                        λv:T.λ:T.eq T t (THead (Bind Abst) w v)
                        λ:T.λw0:T.ty3 g c w w0
                        λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                        λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
             case or3_intro2 : H4:ex3_2 TList nat λws:TList.λi:nat.eq T t (THeads (Flat Appl) ws (TLRef i)) λws:TList.λ:nat.nfs2 c ws λ:TList.λi:nat.nf2 c (TLRef i) 
                the thesis becomes 
                ex4_2
                  T
                  T
                  λv:T.λ:T.eq T t (THead (Bind Abst) w v)
                  λ:T.λw0:T.ty3 g c w w0
                  λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                  λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                   we proceed by induction on H4 to prove 
                      ex4_2
                        T
                        T
                        λv:T.λ:T.eq T t (THead (Bind Abst) w v)
                        λ:T.λw0:T.ty3 g c w w0
                        λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                        λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                      case ex3_2_intro : x0:TList x1:nat H5:eq T t (THeads (Flat Appl) x0 (TLRef x1)) :nfs2 c x0 H7:nf2 c (TLRef x1) 
                         the thesis becomes 
                         ex4_2
                           T
                           T
                           λv:T.λ:T.eq T t (THead (Bind Abst) w v)
                           λ:T.λw0:T.ty3 g c w w0
                           λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                           λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                            (H8
                               we proceed by induction on H5 to prove ty3 g c (THeads (Flat Appl) x0 (TLRef x1)) (THead (Bind Abst) w u)
                                  case refl_equal : 
                                     the thesis becomes the hypothesis H
ty3 g c (THeads (Flat Appl) x0 (TLRef x1)) (THead (Bind Abst) w u)
                            end of H8
                            (H9consider H2
                            (H10consider H8
                            we proceed by induction on x0 to prove 
                               x:T
                                 .x2:T
                                   .ty3 g c (THeads (Flat Appl) x0 (TLRef x1)) (THead (Bind Abst) x x2)
                                     (ty3_nf2_inv_abst_premise c x x2
                                          (ex4_2
                                               T
                                               T
                                               λv:T
                                                 .λ:T
                                                   .eq T (THeads (Flat Appl) x0 (TLRef x1)) (THead (Bind Abst) x v)
                                               λ:T.λw0:T.ty3 g c x w0
                                               λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                               λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v))
                               case TNil : 
                                  the thesis becomes 
                                  x:T
                                    .x2:T
                                      .(ty3
                                          g
                                          c
                                          THeads (Flat ApplTNil (TLRef x1)
                                          THead (Bind Abst) x x2)
                                        (ty3_nf2_inv_abst_premise c x x2
                                             (ex4_2
                                                  T
                                                  T
                                                  λv:T
                                                    .λ:T
                                                      .eq
                                                        T
                                                        THeads (Flat ApplTNil (TLRef x1)
                                                        THead (Bind Abst) x v
                                                  λ:T.λw0:T.ty3 g c x w0
                                                  λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                  λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v))
                                      assume xT
                                      assume x2T
                                        we must prove 
                                              (ty3
                                                  g
                                                  c
                                                  THeads (Flat ApplTNil (TLRef x1)
                                                  THead (Bind Abst) x x2)
                                                (ty3_nf2_inv_abst_premise c x x2
                                                     (ex4_2
                                                          T
                                                          T
                                                          λv:T
                                                            .λ:T
                                                              .eq
                                                                T
                                                                THeads (Flat ApplTNil (TLRef x1)
                                                                THead (Bind Abst) x v
                                                          λ:T.λw0:T.ty3 g c x w0
                                                          λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                          λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v))
                                        or equivalently 
                                              ty3 g c (TLRef x1) (THead (Bind Abst) x x2)
                                                (ty3_nf2_inv_abst_premise c x x2
                                                     (ex4_2
                                                          T
                                                          T
                                                          λv:T
                                                            .λ:T
                                                              .eq
                                                                T
                                                                THeads (Flat ApplTNil (TLRef x1)
                                                                THead (Bind Abst) x v
                                                          λ:T.λw0:T.ty3 g c x w0
                                                          λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                          λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v))
                                         suppose H11ty3 g c (TLRef x1) (THead (Bind Abst) x x2)
                                         suppose H12ty3_nf2_inv_abst_premise c x x2
                                           by (ty3_gen_lref . . . . H11)
                                           we proved 
                                              or
                                                ex3_3
                                                  C
                                                  T
                                                  T
                                                  λ:C.λ:T.λt:T.pc3 c (lift (S x1) O t) (THead (Bind Abst) x x2)
                                                  λe:C.λu:T.λ:T.getl x1 c (CHead e (Bind Abbr) u)
                                                  λe:C.λu:T.λt:T.ty3 g e u t
                                                ex3_3
                                                  C
                                                  T
                                                  T
                                                  λ:C.λu:T.λ:T.pc3 c (lift (S x1) O u) (THead (Bind Abst) x x2)
                                                  λe:C.λu:T.λ:T.getl x1 c (CHead e (Bind Abst) u)
                                                  λe:C.λu:T.λt:T.ty3 g e u t
                                           we proceed by induction on the previous result to prove 
                                              ex4_2
                                                T
                                                T
                                                λv:T.λ:T.eq T (TLRef x1) (THead (Bind Abst) x v)
                                                λ:T.λw0:T.ty3 g c x w0
                                                λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v
                                              case or_introl : H13:ex3_3 C T T λ:C.λ:T.λt0:T.pc3 c (lift (S x1) O t0) (THead (Bind Abst) x x2) λe:C.λu0:T.λ:T.getl x1 c (CHead e (Bind Abbr) u0) λe:C.λu0:T.λt0:T.ty3 g e u0 t0 
                                                 the thesis becomes 
                                                 ex4_2
                                                   T
                                                   T
                                                   λv:T.λ:T.eq T (TLRef x1) (THead (Bind Abst) x v)
                                                   λ:T.λw0:T.ty3 g c x w0
                                                   λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                   λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v
                                                    we proceed by induction on H13 to prove 
                                                       ex4_2
                                                         T
                                                         T
                                                         λv:T.λ:T.eq T (TLRef x1) (THead (Bind Abst) x v)
                                                         λ:T.λw0:T.ty3 g c x w0
                                                         λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                         λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v
                                                       case ex3_3_intro : x3:C x4:T x5:T :pc3 c (lift (S x1) O x5) (THead (Bind Abst) x x2) H15:getl x1 c (CHead x3 (Bind Abbr) x4) :ty3 g x3 x4 x5 
                                                          the thesis becomes 
                                                          ex4_2
                                                            T
                                                            T
                                                            λv:T.λ:T.eq T (TLRef x1) (THead (Bind Abst) x v)
                                                            λ:T.λw0:T.ty3 g c x w0
                                                            λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                            λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v
                                                             by (nf2_gen_lref . . . . H15 H7 .)

                                                                ex4_2
                                                                  T
                                                                  T
                                                                  λv:T.λ:T.eq T (TLRef x1) (THead (Bind Abst) x v)
                                                                  λ:T.λw0:T.ty3 g c x w0
                                                                  λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                                  λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v

                                                       ex4_2
                                                         T
                                                         T
                                                         λv:T.λ:T.eq T (TLRef x1) (THead (Bind Abst) x v)
                                                         λ:T.λw0:T.ty3 g c x w0
                                                         λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                         λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v
                                              case or_intror : H13:ex3_3 C T T λ:C.λu0:T.λ:T.pc3 c (lift (S x1) O u0) (THead (Bind Abst) x x2) λe:C.λu0:T.λ:T.getl x1 c (CHead e (Bind Abst) u0) λe:C.λu0:T.λt0:T.ty3 g e u0 t0 
                                                 the thesis becomes 
                                                 ex4_2
                                                   T
                                                   T
                                                   λv:T.λ:T.eq T (TLRef x1) (THead (Bind Abst) x v)
                                                   λ:T.λw0:T.ty3 g c x w0
                                                   λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                   λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v
                                                    we proceed by induction on H13 to prove 
                                                       ex4_2
                                                         T
                                                         T
                                                         λv:T.λ:T.eq T (TLRef x1) (THead (Bind Abst) x v)
                                                         λ:T.λw0:T.ty3 g c x w0
                                                         λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                         λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v
                                                       case ex3_3_intro : x3:C x4:T x5:T H14:pc3 c (lift (S x1) O x4) (THead (Bind Abst) x x2) H15:getl x1 c (CHead x3 (Bind Abst) x4) :ty3 g x3 x4 x5 
                                                          the thesis becomes 
                                                          ex4_2
                                                            T
                                                            T
                                                            λv:T.λ:T.eq T (TLRef x1) (THead (Bind Abst) x v)
                                                            λ:T.λw0:T.ty3 g c x w0
                                                            λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                            λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v
                                                             (H_x0
                                                                consider H14
                                                                we proved pc3 c (lift (S x1) O x4) (THead (Bind Abst) x x2)
                                                                that is equivalent to 
                                                                   pc3
                                                                     c
                                                                     THeads (Flat ApplTNil (lift (S x1) O x4)
                                                                     THead (Bind Abst) x x2
                                                                by (H12 . . . H15 . previous)
False
                                                             end of H_x0
                                                             (H17consider H_x0
                                                             we proceed by induction on H17 to prove 
                                                                ex4_2
                                                                  T
                                                                  T
                                                                  λv:T.λ:T.eq T (TLRef x1) (THead (Bind Abst) x v)
                                                                  λ:T.λw0:T.ty3 g c x w0
                                                                  λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                                  λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v

                                                                ex4_2
                                                                  T
                                                                  T
                                                                  λv:T.λ:T.eq T (TLRef x1) (THead (Bind Abst) x v)
                                                                  λ:T.λw0:T.ty3 g c x w0
                                                                  λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                                  λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v

                                                       ex4_2
                                                         T
                                                         T
                                                         λv:T.λ:T.eq T (TLRef x1) (THead (Bind Abst) x v)
                                                         λ:T.λw0:T.ty3 g c x w0
                                                         λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                         λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v
                                           we proved 
                                              ex4_2
                                                T
                                                T
                                                λv:T.λ:T.eq T (TLRef x1) (THead (Bind Abst) x v)
                                                λ:T.λw0:T.ty3 g c x w0
                                                λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v
                                           that is equivalent to 
                                              ex4_2
                                                T
                                                T
                                                λv:T
                                                  .λ:T
                                                    .eq
                                                      T
                                                      THeads (Flat ApplTNil (TLRef x1)
                                                      THead (Bind Abst) x v
                                                λ:T.λw0:T.ty3 g c x w0
                                                λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v
                                        we proved 
                                           ty3 g c (TLRef x1) (THead (Bind Abst) x x2)
                                             (ty3_nf2_inv_abst_premise c x x2
                                                  (ex4_2
                                                       T
                                                       T
                                                       λv:T
                                                         .λ:T
                                                           .eq
                                                             T
                                                             THeads (Flat ApplTNil (TLRef x1)
                                                             THead (Bind Abst) x v
                                                       λ:T.λw0:T.ty3 g c x w0
                                                       λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                       λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v))
                                        that is equivalent to 
                                           (ty3
                                               g
                                               c
                                               THeads (Flat ApplTNil (TLRef x1)
                                               THead (Bind Abst) x x2)
                                             (ty3_nf2_inv_abst_premise c x x2
                                                  (ex4_2
                                                       T
                                                       T
                                                       λv:T
                                                         .λ:T
                                                           .eq
                                                             T
                                                             THeads (Flat ApplTNil (TLRef x1)
                                                             THead (Bind Abst) x v
                                                       λ:T.λw0:T.ty3 g c x w0
                                                       λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                       λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v))

                                        x:T
                                          .x2:T
                                            .(ty3
                                                g
                                                c
                                                THeads (Flat ApplTNil (TLRef x1)
                                                THead (Bind Abst) x x2)
                                              (ty3_nf2_inv_abst_premise c x x2
                                                   (ex4_2
                                                        T
                                                        T
                                                        λv:T
                                                          .λ:T
                                                            .eq
                                                              T
                                                              THeads (Flat ApplTNil (TLRef x1)
                                                              THead (Bind Abst) x v
                                                        λ:T.λw0:T.ty3 g c x w0
                                                        λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                        λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v))
                               case TCons : t0:T t1:TList 
                                  the thesis becomes 
                                  x:T
                                    .x2:T
                                      .(ty3
                                          g
                                          c
                                          THeads (Flat Appl) (TCons t0 t1) (TLRef x1)
                                          THead (Bind Abst) x x2)
                                        (ty3_nf2_inv_abst_premise c x x2
                                             (ex4_2
                                                  T
                                                  T
                                                  λv:T
                                                    .λ:T
                                                      .eq
                                                        T
                                                        THeads (Flat Appl) (TCons t0 t1) (TLRef x1)
                                                        THead (Bind Abst) x v
                                                  λ:T.λw0:T.ty3 g c x w0
                                                  λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                  λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v))
                                  (H11) by induction hypothesis we know 
                                     x:T
                                       .x2:T
                                         .ty3 g c (THeads (Flat Appl) t1 (TLRef x1)) (THead (Bind Abst) x x2)
                                           (ty3_nf2_inv_abst_premise c x x2
                                                (ex4_2
                                                     T
                                                     T
                                                     λv:T
                                                       .λ:T
                                                         .eq T (THeads (Flat Appl) t1 (TLRef x1)) (THead (Bind Abst) x v)
                                                     λ:T.λw0:T.ty3 g c x w0
                                                     λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                     λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v))
                                      assume xT
                                      assume x2T
                                        we must prove 
                                              (ty3
                                                  g
                                                  c
                                                  THeads (Flat Appl) (TCons t0 t1) (TLRef x1)
                                                  THead (Bind Abst) x x2)
                                                (ty3_nf2_inv_abst_premise c x x2
                                                     (ex4_2
                                                          T
                                                          T
                                                          λv:T
                                                            .λ:T
                                                              .eq
                                                                T
                                                                THeads (Flat Appl) (TCons t0 t1) (TLRef x1)
                                                                THead (Bind Abst) x v
                                                          λ:T.λw0:T.ty3 g c x w0
                                                          λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                          λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v))
                                        or equivalently 
                                              (ty3
                                                  g
                                                  c
                                                  THead (Flat Appl) t0 (THeads (Flat Appl) t1 (TLRef x1))
                                                  THead (Bind Abst) x x2)
                                                (ty3_nf2_inv_abst_premise c x x2
                                                     (ex4_2
                                                          T
                                                          T
                                                          λv:T
                                                            .λ:T
                                                              .eq
                                                                T
                                                                THeads (Flat Appl) (TCons t0 t1) (TLRef x1)
                                                                THead (Bind Abst) x v
                                                          λ:T.λw0:T.ty3 g c x w0
                                                          λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                          λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v))
                                         suppose H12
                                            ty3
                                              g
                                              c
                                              THead (Flat Appl) t0 (THeads (Flat Appl) t1 (TLRef x1))
                                              THead (Bind Abst) x x2
                                         suppose H13ty3_nf2_inv_abst_premise c x x2
                                           by (ty3_gen_appl . . . . . H12)
                                           we proved 
                                              ex3_2
                                                T
                                                T
                                                λu:T
                                                  .λt:T
                                                    .pc3
                                                      c
                                                      THead (Flat Appl) t0 (THead (Bind Abst) u t)
                                                      THead (Bind Abst) x x2
                                                λu:T
                                                  .λt:T
                                                    .ty3 g c (THeads (Flat Appl) t1 (TLRef x1)) (THead (Bind Abst) u t)
                                                λu:T.λ:T.ty3 g c t0 u
                                           we proceed by induction on the previous result to prove 
                                              ex4_2
                                                T
                                                T
                                                λv:T
                                                  .λ:T
                                                    .eq
                                                      T
                                                      THead (Flat Appl) t0 (THeads (Flat Appl) t1 (TLRef x1))
                                                      THead (Bind Abst) x v
                                                λ:T.λw0:T.ty3 g c x w0
                                                λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v
                                              case ex3_2_intro : x3:T x4:T H14:pc3 c (THead (Flat Appl) t0 (THead (Bind Abst) x3 x4)) (THead (Bind Abst) x x2) H15:ty3 g c (THeads (Flat Appl) t1 (TLRef x1)) (THead (Bind Abst) x3 x4) :ty3 g c t0 x3 
                                                 the thesis becomes 
                                                 ex4_2
                                                   T
                                                   T
                                                   λv:T
                                                     .λ:T
                                                       .eq
                                                         T
                                                         THead (Flat Appl) t0 (THeads (Flat Appl) t1 (TLRef x1))
                                                         THead (Bind Abst) x v
                                                   λ:T.λw0:T.ty3 g c x w0
                                                   λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                   λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v
                                                    (H_y
                                                       by (ty3_nf2_gen__ty3_nf2_inv_abst_aux . . . H13 . . . H14)
ty3_nf2_inv_abst_premise c x3 x4
                                                    end of H_y
                                                    (H_x0
                                                       by (H11 . . H15 H_y)

                                                          ex4_2
                                                            T
                                                            T
                                                            λv:T
                                                              .λ:T.eq T (THeads (Flat Appl) t1 (TLRef x1)) (THead (Bind Abst) x3 v)
                                                            λ:T.λw0:T.ty3 g c x3 w0
                                                            λv:T.λ:T.ty3 g (CHead c (Bind Abst) x3) v x4
                                                            λv:T.λ:T.nf2 (CHead c (Bind Abst) x3) v
                                                    end of H_x0
                                                    (H17consider H_x0
                                                    we proceed by induction on H17 to prove 
                                                       ex4_2
                                                         T
                                                         T
                                                         λv:T
                                                           .λ:T
                                                             .eq
                                                               T
                                                               THead (Flat Appl) t0 (THeads (Flat Appl) t1 (TLRef x1))
                                                               THead (Bind Abst) x v
                                                         λ:T.λw0:T.ty3 g c x w0
                                                         λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                         λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v
                                                       case ex4_2_intro : x5:T x6:T H18:eq T (THeads (Flat Appl) t1 (TLRef x1)) (THead (Bind Abst) x3 x5) :ty3 g c x3 x6 :ty3 g (CHead c (Bind Abst) x3) x5 x4 :nf2 (CHead c (Bind Abst) x3) x5 
                                                          the thesis becomes 
                                                          ex4_2
                                                            T
                                                            T
                                                            λv:T
                                                              .λ:T
                                                                .eq
                                                                  T
                                                                  THead (Flat Appl) t0 (THeads (Flat Appl) t1 (TLRef x1))
                                                                  THead (Bind Abst) x v
                                                            λ:T.λw0:T.ty3 g c x w0
                                                            λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                            λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v
                                                             suppose H22
                                                                eq
                                                                  T
                                                                  THeads (Flat ApplTNil (TLRef x1)
                                                                  THead (Bind Abst) x3 x5
                                                                (H23
                                                                   consider H22
                                                                   we proved 
                                                                      eq
                                                                        T
                                                                        THeads (Flat ApplTNil (TLRef x1)
                                                                        THead (Bind Abst) x3 x5
                                                                   that is equivalent to eq T (TLRef x1) (THead (Bind Abst) x3 x5)
                                                                   we proceed by induction on the previous result to prove 
                                                                      <λ:T.Prop>
                                                                        CASE THead (Bind Abst) x3 x5 OF
                                                                          TSort False
                                                                        | TLRef True
                                                                        | THead   False
                                                                      case refl_equal : 
                                                                         the thesis becomes 
                                                                         <λ:T.Prop>
                                                                           CASE TLRef x1 OF
                                                                             TSort False
                                                                           | TLRef True
                                                                           | THead   False
                                                                            consider I
                                                                            we proved True

                                                                               <λ:T.Prop>
                                                                                 CASE TLRef x1 OF
                                                                                   TSort False
                                                                                 | TLRef True
                                                                                 | THead   False

                                                                      <λ:T.Prop>
                                                                        CASE THead (Bind Abst) x3 x5 OF
                                                                          TSort False
                                                                        | TLRef True
                                                                        | THead   False
                                                                end of H23
                                                                consider H23
                                                                we proved 
                                                                   <λ:T.Prop>
                                                                     CASE THead (Bind Abst) x3 x5 OF
                                                                       TSort False
                                                                     | TLRef True
                                                                     | THead   False
                                                                that is equivalent to False
                                                                we proceed by induction on the previous result to prove 
                                                                   ex4_2
                                                                     T
                                                                     T
                                                                     λv:T
                                                                       .λ:T
                                                                         .eq
                                                                           T
                                                                           THead (Flat Appl) t0 (THeads (Flat ApplTNil (TLRef x1))
                                                                           THead (Bind Abst) x v
                                                                     λ:T.λw0:T.ty3 g c x w0
                                                                     λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                                     λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v
                                                                we proved 
                                                                   ex4_2
                                                                     T
                                                                     T
                                                                     λv:T
                                                                       .λ:T
                                                                         .eq
                                                                           T
                                                                           THead (Flat Appl) t0 (THeads (Flat ApplTNil (TLRef x1))
                                                                           THead (Bind Abst) x v
                                                                     λ:T.λw0:T.ty3 g c x w0
                                                                     λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                                     λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v

                                                                (eq
                                                                    T
                                                                    THeads (Flat ApplTNil (TLRef x1)
                                                                    THead (Bind Abst) x3 x5)
                                                                  (ex4_2
                                                                       T
                                                                       T
                                                                       λv:T
                                                                         .λ:T
                                                                           .eq
                                                                             T
                                                                             THead (Flat Appl) t0 (THeads (Flat ApplTNil (TLRef x1))
                                                                             THead (Bind Abst) x v
                                                                       λ:T.λw0:T.ty3 g c x w0
                                                                       λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                                       λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v)
                                                              assume t2T
                                                              assume t3TList
                                                                 suppose 
                                                                    eq T (THeads (Flat Appl) t3 (TLRef x1)) (THead (Bind Abst) x3 x5)
                                                                      (ex4_2
                                                                           T
                                                                           T
                                                                           λv:T
                                                                             .λ:T
                                                                               .eq
                                                                                 T
                                                                                 THead (Flat Appl) t0 (THeads (Flat Appl) t3 (TLRef x1))
                                                                                 THead (Bind Abst) x v
                                                                           λ:T.λw0:T.ty3 g c x w0
                                                                           λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                                           λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v)
                                                                suppose H22
                                                                   eq
                                                                     T
                                                                     THeads (Flat Appl) (TCons t2 t3) (TLRef x1)
                                                                     THead (Bind Abst) x3 x5
                                                                   (H23
                                                                      consider H22
                                                                      we proved 
                                                                         eq
                                                                           T
                                                                           THeads (Flat Appl) (TCons t2 t3) (TLRef x1)
                                                                           THead (Bind Abst) x3 x5
                                                                      that is equivalent to 
                                                                         eq
                                                                           T
                                                                           THead (Flat Appl) t2 (THeads (Flat Appl) t3 (TLRef x1))
                                                                           THead (Bind Abst) x3 x5
                                                                      we proceed by induction on the previous result to prove 
                                                                         <λ:T.Prop>
                                                                           CASE THead (Bind Abst) x3 x5 OF
                                                                             TSort False
                                                                           | TLRef False
                                                                           | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True
                                                                         case refl_equal : 
                                                                            the thesis becomes 
                                                                            <λ:T.Prop>
                                                                              CASE THead (Flat Appl) t2 (THeads (Flat Appl) t3 (TLRef x1)) OF
                                                                                TSort False
                                                                              | TLRef False
                                                                              | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True
                                                                               consider I
                                                                               we proved True

                                                                                  <λ:T.Prop>
                                                                                    CASE THead (Flat Appl) t2 (THeads (Flat Appl) t3 (TLRef x1)) OF
                                                                                      TSort False
                                                                                    | TLRef False
                                                                                    | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True

                                                                         <λ:T.Prop>
                                                                           CASE THead (Bind Abst) x3 x5 OF
                                                                             TSort False
                                                                           | TLRef False
                                                                           | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True
                                                                   end of H23
                                                                   consider H23
                                                                   we proved 
                                                                      <λ:T.Prop>
                                                                        CASE THead (Bind Abst) x3 x5 OF
                                                                          TSort False
                                                                        | TLRef False
                                                                        | THead k  <λ:K.Prop> CASE k OF Bind False | Flat True
                                                                   that is equivalent to False
                                                                   we proceed by induction on the previous result to prove 
                                                                      ex4_2
                                                                        T
                                                                        T
                                                                        λv:T
                                                                          .λ:T
                                                                            .eq
                                                                              T
                                                                              THead (Flat Appl) t0 (THeads (Flat Appl) (TCons t2 t3) (TLRef x1))
                                                                              THead (Bind Abst) x v
                                                                        λ:T.λw0:T.ty3 g c x w0
                                                                        λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                                        λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v
                                                                   we proved 
                                                                      ex4_2
                                                                        T
                                                                        T
                                                                        λv:T
                                                                          .λ:T
                                                                            .eq
                                                                              T
                                                                              THead (Flat Appl) t0 (THeads (Flat Appl) (TCons t2 t3) (TLRef x1))
                                                                              THead (Bind Abst) x v
                                                                        λ:T.λw0:T.ty3 g c x w0
                                                                        λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                                        λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v

                                                                   H22:eq
                                                                                T
                                                                                THeads (Flat Appl) (TCons t2 t3) (TLRef x1)
                                                                                THead (Bind Abst) x3 x5
                                                                     .ex4_2
                                                                       T
                                                                       T
                                                                       λv:T
                                                                         .λ:T
                                                                           .eq
                                                                             T
                                                                             THead (Flat Appl) t0 (THeads (Flat Appl) (TCons t2 t3) (TLRef x1))
                                                                             THead (Bind Abst) x v
                                                                       λ:T.λw0:T.ty3 g c x w0
                                                                       λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                                       λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v
                                                             by (previous . H18)

                                                                ex4_2
                                                                  T
                                                                  T
                                                                  λv:T
                                                                    .λ:T
                                                                      .eq
                                                                        T
                                                                        THead (Flat Appl) t0 (THeads (Flat Appl) t1 (TLRef x1))
                                                                        THead (Bind Abst) x v
                                                                  λ:T.λw0:T.ty3 g c x w0
                                                                  λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                                  λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v

                                                       ex4_2
                                                         T
                                                         T
                                                         λv:T
                                                           .λ:T
                                                             .eq
                                                               T
                                                               THead (Flat Appl) t0 (THeads (Flat Appl) t1 (TLRef x1))
                                                               THead (Bind Abst) x v
                                                         λ:T.λw0:T.ty3 g c x w0
                                                         λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                         λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v
                                           we proved 
                                              ex4_2
                                                T
                                                T
                                                λv:T
                                                  .λ:T
                                                    .eq
                                                      T
                                                      THead (Flat Appl) t0 (THeads (Flat Appl) t1 (TLRef x1))
                                                      THead (Bind Abst) x v
                                                λ:T.λw0:T.ty3 g c x w0
                                                λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v
                                           that is equivalent to 
                                              ex4_2
                                                T
                                                T
                                                λv:T
                                                  .λ:T
                                                    .eq
                                                      T
                                                      THeads (Flat Appl) (TCons t0 t1) (TLRef x1)
                                                      THead (Bind Abst) x v
                                                λ:T.λw0:T.ty3 g c x w0
                                                λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v
                                        we proved 
                                           (ty3
                                               g
                                               c
                                               THead (Flat Appl) t0 (THeads (Flat Appl) t1 (TLRef x1))
                                               THead (Bind Abst) x x2)
                                             (ty3_nf2_inv_abst_premise c x x2
                                                  (ex4_2
                                                       T
                                                       T
                                                       λv:T
                                                         .λ:T
                                                           .eq
                                                             T
                                                             THeads (Flat Appl) (TCons t0 t1) (TLRef x1)
                                                             THead (Bind Abst) x v
                                                       λ:T.λw0:T.ty3 g c x w0
                                                       λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                       λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v))
                                        that is equivalent to 
                                           (ty3
                                               g
                                               c
                                               THeads (Flat Appl) (TCons t0 t1) (TLRef x1)
                                               THead (Bind Abst) x x2)
                                             (ty3_nf2_inv_abst_premise c x x2
                                                  (ex4_2
                                                       T
                                                       T
                                                       λv:T
                                                         .λ:T
                                                           .eq
                                                             T
                                                             THeads (Flat Appl) (TCons t0 t1) (TLRef x1)
                                                             THead (Bind Abst) x v
                                                       λ:T.λw0:T.ty3 g c x w0
                                                       λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                       λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v))

                                        x:T
                                          .x2:T
                                            .(ty3
                                                g
                                                c
                                                THeads (Flat Appl) (TCons t0 t1) (TLRef x1)
                                                THead (Bind Abst) x x2)
                                              (ty3_nf2_inv_abst_premise c x x2
                                                   (ex4_2
                                                        T
                                                        T
                                                        λv:T
                                                          .λ:T
                                                            .eq
                                                              T
                                                              THeads (Flat Appl) (TCons t0 t1) (TLRef x1)
                                                              THead (Bind Abst) x v
                                                        λ:T.λw0:T.ty3 g c x w0
                                                        λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                                        λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v))
                            we proved 
                               x:T
                                 .x2:T
                                   .ty3 g c (THeads (Flat Appl) x0 (TLRef x1)) (THead (Bind Abst) x x2)
                                     (ty3_nf2_inv_abst_premise c x x2
                                          (ex4_2
                                               T
                                               T
                                               λv:T
                                                 .λ:T
                                                   .eq T (THeads (Flat Appl) x0 (TLRef x1)) (THead (Bind Abst) x v)
                                               λ:T.λw0:T.ty3 g c x w0
                                               λv:T.λ:T.ty3 g (CHead c (Bind Abst) x) v x2
                                               λv:T.λ:T.nf2 (CHead c (Bind Abst) x) v))
                            by (unintro . . . previous)
                            we proved 
                               x:T
                                 .ty3 g c (THeads (Flat Appl) x0 (TLRef x1)) (THead (Bind Abst) w x)
                                   (ty3_nf2_inv_abst_premise c w x
                                        (ex4_2
                                             T
                                             T
                                             λv:T
                                               .λ:T
                                                 .eq T (THeads (Flat Appl) x0 (TLRef x1)) (THead (Bind Abst) w v)
                                             λ:T.λw0:T.ty3 g c w w0
                                             λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v x
                                             λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v))
                            by (unintro . . . previous H10)
                            we proved 
                               ty3_nf2_inv_abst_premise c w u
                                 (ex4_2
                                      T
                                      T
                                      λv:T
                                        .λ:T
                                          .eq T (THeads (Flat Appl) x0 (TLRef x1)) (THead (Bind Abst) w v)
                                      λ:T.λw0:T.ty3 g c w w0
                                      λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                      λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v)
                            by (previous H9)
                            we proved 
                               ex4_2
                                 T
                                 T
                                 λv:T
                                   .λ:T
                                     .eq T (THeads (Flat Appl) x0 (TLRef x1)) (THead (Bind Abst) w v)
                                 λ:T.λw0:T.ty3 g c w w0
                                 λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                 λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
                            by (eq_ind_r . . . previous . H5)

                               ex4_2
                                 T
                                 T
                                 λv:T.λ:T.eq T t (THead (Bind Abst) w v)
                                 λ:T.λw0:T.ty3 g c w w0
                                 λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                 λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v

                      ex4_2
                        T
                        T
                        λv:T.λ:T.eq T t (THead (Bind Abst) w v)
                        λ:T.λw0:T.ty3 g c w w0
                        λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                        λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
          we proved 
             ex4_2
               T
               T
               λv:T.λ:T.eq T t (THead (Bind Abst) w v)
               λ:T.λw0:T.ty3 g c w w0
               λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
               λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v
       we proved 
          g:G
            .c:C
              .t:T
                .w:T
                  .u:T
                    .ty3 g c t (THead (Bind Abst) w u)
                      (nf2 c t
                           (nf2 c w
                                (ty3_nf2_inv_abst_premise c w u
                                     (ex4_2
                                          T
                                          T
                                          λv:T.λ:T.eq T t (THead (Bind Abst) w v)
                                          λ:T.λw0:T.ty3 g c w w0
                                          λv:T.λ:T.ty3 g (CHead c (Bind Abst) w) v u
                                          λv:T.λ:T.nf2 (CHead c (Bind Abst) w) v))))