Let C be a root class of groups, i. e. , a class containing nontrivial groups and closed under taking subgroups and Cartesian wreath products. Let also P be a tree product of groups such that each edge subgroup of P is normal in the vertex group that includes it. The paper presents several sufficient conditions for the existence of a homomorphism from the group P onto a C -group that is injective on all vertex groups. Some sufficient conditions for the C -residuality of the group P are also proved.
Sokolov et al. (Thu,) studied this question.