Bifurcation of limit cycles from a center in two-parameter system

In this paper we consider a two-parameter perturbated system which takes the systems discussed in [1], [2], [3] as its special case. The bifurcation region of the limit cycles is given on the parameter plane. The author also studies the stability of the limit cycles. At the end of this paper the author discusses the difference of the bifurcation of the limit cycles from a center between the case of two-parameter and the case of one-parameter.