proposition: Lemma nf_subterm alpha beta : subterm alpha beta -> nf beta -> nf alpha.
proof: Proof. induction 1; intros; try nf_inv; auto. Qed.
imports: Coq(Arith List Lia Compare_dec Relations Wellfounded RelationClasses) hydras(Epsilon0) hydras(More_Arith Restriction) hydras(ON_Generic) hydras(rpo.term rpo.rpo) hydras(T2) hydras(Compat815)