Foldings, Graphs of Groups and the Membership Problem.

Ilya Kapovich Richard Weidmann Alexei G. Myasnikov Foldings, Graphs of Groups and the Membership Problem. 95-128 2005 15 IJAC 1 http://dx.doi.org/10.1142/S021819670500213X db/journals/ijac/ijac15.html#KapovichWM05