1. Lexicographic matching in Boolean algebras,;Aigner;J. Comb. Th. (B),1973
2. The use of symmetry for finding the width of a partially ordered set,;Alekseev;(Russian) Diskret. Analiz.,1974
3. A generalization of Sperner's lemma,;Baker;J. Comb. Th.,1969
4. X. Berenguer, J. Diaz, and L. H. Harper, “A solution of the Sperner-Erdös problem,” preprint.
5. On the set of divisors of a number,;de Bruijn;Nieuw. Arch. Wisk, (2),1952