fact: Definition least_cardinal_ext {X : Type} (P : Family X) {Y : Type} (V : Ensemble Y) := least_cardinal (fun Z W => exists U : Ensemble X, In P U /\ eq_cardinal_ens U W) V.
imports: Coq(ClassicalChoice Description Lia PeanoNat Program.Subset) ZornsLemma(Cardinals CountableTypes CSB DecidableDec Families Finite_sets FiniteTypes FunctionProperties FunctionPropertiesEns InverseImage Powerset_facts Proj1SigInjective ReverseMath.AddSubtract) Coq(RelationClasses)