proposition: Lemma existI (T : System) (f : Formula) (v : nat) (t : Term): SysPrf T (substF f v t) -> SysPrf T (exH v, f)%fol.
proof: Proof. apply (existI LNN). Qed.
imports: Coq(Arith Ensembles List) LibHyps(LibHyps) hydras(MoreLibHyps NewNotations)