摘要： We discuss the existence and the number of periodic solutions of differential equation dx/dt=A1（t）x+A2（t）x2+A3（t）x3/a0（t）+a1（t）x+a2（t）x2 （1）where Ai（t）, aj（t） （i=1,2,3;j=0,1,2） are continuous periodic functions. The results of this paper extend the work of paper [1].
