On residually finite graph products
Baumslag (1963) gave a famous criterion, in terms of filtrations, for an amalgamated free product of two groups to be residually finite. The concept of the fundamental group of a graph of groups generalizes the idea of amalgamated free product, and sufficient conditions for such a ``graph product'' to be residually finite are given in this paper. While essentially simple, based on a ``filtration'' using families of subgroups of the vertex groups, the conditions are notationally too complex to outline here.
scientific article; zbMATH DE number 4059687