fact: Definition least_cardinal_subset {X : Type} (P : Family X) (U : Ensemble X) : Prop := In P U /\ forall V : Ensemble X, In P V -> le_cardinal_ens U 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)