系统(E)的极限环的不存在性

Non-Existence of Limit Cycle of the System(E)

本文在文献［２］的基础上继续对系统（Ｅ）进行了定性分析，解决了正平衡点中心———焦点的判定问题及其外围极限环的不存在性，同时纠正了文献［２］中的一个错误。

On the basis literature of paper ,the author continues the study on the systems (E) qualitative analysis and get further result.In particular, the problem determinating of center of point singularity-focus is solved,and the non-existence of outside limit cycle is discussed. In addition a mistake in ] is corrected.