Bifurcations of Limit Circles and Center Conditions for a Class of Non-analytic Cubic <em>Z</em><sub>2</sub> Polynomial Differential Systems

Feng LI, Yi Rong LIU, Yin Lai JIN

Acta Mathematica Sinica . 2012, (11): 2275 -2288 . DOI: 10.1007/s10114-012-0454-z