1. The precise center of a crossed module;Arias;J. Group Theory,2009
2. Representations of groups as quotient groups, I, II, III;Baer;Trans. Am. Math. Soc.,1945
3. Group Extensions, Representations, and the Schur Multiplier;Beyl,1982
4. Van Kampen theorems for diagrams of spaces;Brown;Topology,1987
5. On the nilpotent multipliers of a group;Burns;Math. Z.,1997