proposition: Lemma mul_divide_cancel_l : forall n m p, p ~= 0 -> ((p * n | p * m) <-> (n | m)).
proof: Proof. intros n m p Hp. split. - intros (q,Hq). exists q. now rewrite mul_shuffle3, mul_cancel_l in Hq. - apply mul_divide_mono_l. Qed.
imports: NZAxioms NZMulOrder