intros d m m' H' H'0; rewrite <- (proj_ok d m); rewrite <- (proj_ok d m');
auto.
Qed.
(* Division is transitive. *)

(* Specifications: *)
Lemma mdiv_trans : forall d : nat, transitive (mon d) (mdiv d).
intros d; elim d; unfold transitive in |- *; auto.