This paper provides the sufficient and necessary conditions for the three dimensional competitive Leslie-Gower system to admit the Hopf bifurcation among Jiang-Niu's classes 26-31[16].Combining the Poincare-Bendixson theorem and the Hopf bifurcation theorem,we present criteria for systems among Jiang-Niu's classes 29-31 to possess at least two limit cycles and give examples to apply them. |