* Axiom of Choice and Its Equivalents at ProvenMath includes formal statement of the Axiom of Choice, Hausdorff's Maximal Principle, Zorn's Lemma and formal proofs of their equivalence down to the finest detail.
==External links==*Axiom of Choice and Its Equivalents at ProvenMath includes formal statement of the Axiom of Choice, Hausdorff's Maximal Principle, Zorn's Lemma and formal proofs of their equivalence down to the finest detail.