关于(Ⅱ)类方程极限环个数问题

ON THE PROBLEM OF THE NUMBER OF LIMIT CYCLES OF SYSTEMS OF TYPE (Ⅱ)

本文利用Ｄｕｌａｃ函数构造（Ⅱ类方程的不变集［１］，研究此类方程极限环的个数，给出了判别准则，回答了文［２］中提出的问题．

in this paper, we construct invariant sets of the systems of the Type (Ⅱ) byusing Dulac functions and study the number of limit cycles of the systems. We obtain somecriteria and answer some questions raised in [2].