proposition: Lemma lt_wf_double_ind : forall P:nat -> nat -> Prop, (forall n m, (forall p (q:nat), p < n -> P p q) -> (forall p, p < m -> P n p) -> P n m) -> forall n m, P n m.
proof: Proof. intros P Hrec p; pattern p; apply lt_wf_ind. intros n H q; pattern q; apply lt_wf_ind; auto. Qed.
imports: PeanoNat