摘要
In a previous paper (Acta Mathematica Sinica Vol. 28 No. 1) we considered the problem of limit cycles from the loop of a saddle-point separatrix that is stable or unstable. We first gave the criterion of stability of this separatrix loop and a sufficient condition of bifurcation of limit cycles. This letter generalizes the result of the previous paper to the ease where the loop contains a center or the loop
