proposition: Lemma nImp (T : System) (f g : Formula): SysPrf T (f /\ ~g)%nt -> SysPrf T (~ (f -> g))%nt.
proof: Proof. apply (nImp LNT). Qed.
imports: Coq(Arith Ensembles List) hydras.Ackermann(Languages folProof folProp folLogic3)