主要讨论系统I极限环存在性相关的问题，文中通过对系统I构造新的外境界线，得到定理a。

We discuss issues of limit cycles' existence about system I. Based on the system I, we construct a new outer boundary line, get Theorem a.

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第48条(建筑线)直辖市、县(市)(局)主管建筑机关，应指定已经公告道路之境界线为建筑线。

Article 48 the municipal and county (city) (bureau) competent authorities of construction shall define the borderlines of the roads already announced as the building lines.

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