ON THE UNIQUENESS OF THE LIMIT CYCLE OF THE QUADRATIC SYSTEM WITH A WEAK FOCUS OF ORDER 2
具有二阶细焦点的二次系统极限环的唯一性

This paper,under fairly general conditions,it is proved that a quadratic system with afocus of order 2 has at most one limit cycle around the weak focus.As a consequence,all theresults of 5] can be deduced from this paper.