proposition: Lemma nf_subterm : forall alpha beta, subterm alpha beta -> nf beta -> nf alpha.
proof: Proof. induction 1; intros; try nf_inv. auto. Qed.
imports: EPSILON0 Arith List Omega Compare_dec Relations Wellfounded Max Tools More_nat AccP not_decreasing EPSILON0 More_nat Gamma0_prelude Gamma0_length term rpo