Groups whose three-generator subgroups are free

Gilbert Baumslag, Peter B. Shalen
1989 Bulletin of the Australian Mathematical Society  
We define a certain class of groups, Cfc, which we show to contain the class of all fc-free groups. Our main theorem shows that certain amalgamated free products of groups in C3 are again in C'3. In the appendix we show that many 3-manifold groups belong to C& for suitable k.
doi:10.1017/s0004972700004275 fatcat:n2rnzryutfbuxocxbumlginloe