DEFINITION pr3_gen_abbr()
TYPE =
       ∀c:C
         .∀u1:T
           .∀t1:T
             .∀x:T
               .pr3 c (THead (Bind Abbr) u1 t1) x
                 →(or
                      ex3_2
                        T
                        T
                        λu2:T.λt2:T.eq T x (THead (Bind Abbr) u2 t2)
                        λu2:T.λ:T.pr3 c u1 u2
                        λ:T.λt2:T.pr3 (CHead c (Bind Abbr) u1) t1 t2
                      pr3 (CHead c (Bind Abbr) u1) t1 (lift (S O) O x))
BODY =
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