DEFINITION pr3_pr0_pr2_t()
TYPE =
       ∀u1:T.∀u2:T.(pr0 u1 u2)→∀c:C.∀t1:T.∀t2:T.∀k:K.(pr2 (CHead c k u2) t1 t2)→(pr3 (CHead c k u1) t1 t2)
BODY =
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