Zhou, Wei et Kim, Goansu, Subgroup separability of certain generalized free products of nilpotent-by-finite groups, Acta mathematica Sinica. English series (Print) , 29(6), 2013, pp. 1199-1204
In this paper, we show that certain generalized free products of nilpotent-by-finite groups are subgroup separable when the amalgamated subgroup is .h..D where D is in the center of both factors.