The Limit Cycles for a Class of Cubic Systems II
一类三次系统的极限环II

The limit cycles for the cubic system $$\begin{array}{ll}&\dot{x}=-y(1-ax)(1-bx)+\delta x-lx^3,\\2mm]&\dot{y}=x(1-c_1x)(1-c_2x)\end{array}$$are discussed. With some conditions of parameters, the existence and uniqueness of limit cycle are given. The obtained results generalize the existing ones.