n times continuously differentiable

In this paper, it is proved that for any positive integer K, ther a exists a planar n-polynomial system which has a series of big limit cycles, and the number of the big limit cycles is at least K.

本文证明了,对任意正整数K,存在平面n次系统,它具有一串不少于K个 大极限环。

The n-pseudo normal subgroups of groups;

“本文引入了群的民;—伪正规子群的概念,并结合文[1]中n次方群及n次方闭群的概念和结果得到若干有益的绪论。