On the Distribution and Number of Limit Cycles for Quadratic Systems with two Foci

Zhang Pingguang

In this paper, we study the distribution and number of limit cycles for quadratic systems with two foci. It is proved that a quadratic system with two foci has at most one limit cycles around one of the two foci, and hence the limit cycles of the quadratic system with two foci must be $(0,1)$--distribution or $(1,i)$-distribution $(i=0, 1, 2, \ldots)$.