Instance Included_proper (V: Type): Proper (Same_set ==> Same_set ==> iff) (@Included V).

Lemma Complement_Included_rev: forall (U: Type) P Q, Included P Q -> Included (Complement U Q) (Complement U P).
Instance Intersection_proper {A}: Proper (Same_set ==> Same_set ==> Same_set) (Intersection A).