proposition: Lemma Intersection_absort_right: forall U (A B: Ensemble U), Included A B -> Same_set (Intersection _ A B) A.
proof: Proof. intros. rewrite Same_set_spec; intro x. rewrite Intersection_spec. specialize (H x); unfold Ensembles.In in H. tauto. Qed.
imports: Coq.Classes.Morphisms Coq.Classes.Equivalence Coq.Sets.Ensembles Coq.Sets.Constructive_sets CertiGraph.lib.Coqlib CertiGraph.lib.EquivDec_ext