proposition: Lemma Assoc_MON : Assoc_law Comp_MON.
proof: Proof. unfold Assoc_law in |- *; simpl in |- *; intros m1 m2 m3 m4 f g h. unfold Equal_MonMor, Ext in |- *; simpl in |- *. unfold Comp_fun in |- *; intro a. apply Refl. Qed.
imports: SET Monoid