(* Collect lemmas that are missing from the Coq stdlib and describe the Ensemble-operations as boolean algebra. Associativity, idempotence, commutativity, complements, distributivity, … *)
From Coq.Sets Require Export Powerset_facts.
From ZornsLemma Require Export EnsemblesImplicit EnsemblesTactics.

Lemma Intersection_associative
{X : Type}
(U V W: Ensemble X) :
Intersection (Intersection U V) W = Intersection U (Intersection V W).