1. Ein Satz uber Untermengen einer endlichen Menge;Sperner;Math. Z.,1928
2. Research problem: “A generalization of Sperner's theorem”;Rota;J. Combin. Theory,1967
3. On a problem of Rota;Canfield;Adv. in Math.,1978
4. A simple counterexample to a conjecture of Rota;Shearer;Discrete Math.,1979
5. Superantichains in the lattice of partitions of a set;Sha;Stud. Appl. Math.,1984