Abstract

Suppose A1,…, An are subsets of a finite set A, and B1,…, Bn are subsets of a finite set B. For each subset S of N = 1, 2,…, n, let As = ∩iϵSAi and \BS\ = ∩iϵSBi. It is shown that if explicit bijections fS:AS → \BS\ for each S ⊆ N are given, an explicit bijection h:A-∪i=1Ai→B-∪i=1Bi can be constructed. The map h is independent of any ordering of the elements of A and B, and of the order in which the subsets Ai and Bi are listed.

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