Combination of fully quasiconvex subgroups and its applications
  In this paper, we state two combination theorems for relatively quasiconvex subgroups in a relatively hyperbolic group. Applications are given to the separability of double cosets of certain relatively quasiconvex subgroups and the existence of closed surface subgroups in relatively hyperbolic groups. 
Wenyuan Yang
math.GR math.GT