proposition: Lemma Intersection2_Included: forall {A} P Q R, Included Q R -> Included (Intersection A P Q) R.
proof: Proof. unfold Included, Ensembles.In. intros. rewrite Intersection_spec in H0. firstorder. Qed.
imports: Coq.Classes.Morphisms Coq.Classes.Equivalence Coq.Sets.Ensembles Coq.Sets.Constructive_sets CertiGraph.lib.Coqlib CertiGraph.lib.EquivDec_ext