Unions of Cockcroft two-complexes
William A. Bogley · Proceedings of the Edinburgh Mathematical Society · 1994
A combinatorial hypothesis is presented that serves as a necessary and sufficient condition for a union of connected Cockcroft two-complexes to be Cockcroft. This combinatorial hypothesis has a component that can be expressed in terms of the second homology of groups. The hypothesis is applied to the study of the third homology of groups.