We modify a previous result, which showed that certain diagrams of spaces are
essentially simplicial monoids, to construct diagrams of spaces which model
simplicial groups. Furthermore, we show that these diagrams can be generalized
to models for Segal groupoids. We then modify Segal's model for simplicial
abelian monoids in such a way that it becomes a model for simplicial abelian
groups.Comment: 24 pages, final version; erratum included at the end. arXiv admin
note: text overlap with arXiv:math/050841