The Subgroups of a Free Product of Two Groups with an Amalgamated Subgroup
The Subgroups of a Free Product of Two Groups with an Amalgamated Subgroup
We prove that all subgroups H of a free product G of two groups A, B with an amalgamated subgroup V are obtained by two constructions from the intersection of H and certain conjugates of A, B, and U.The constructions are those of a tree product, a special kind of …