New criteria are established for upper bounds on the number of limit cycles of periodic Abel differential equations having two periodic invariant curves, one of them bounded. The criteria are applied to obtain upper bounds of either zero or one limit cycle for planar differential systems.

中文翻译：

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具有不变曲线的阿贝尔微分方程中极限环的上界

为具有两条周期性不变曲线的周期性阿贝尔微分方程的极限环数的上限建立了新标准，其中一条有界。应用这些标准来获得平面微分系统的零或一个极限环的上限。