Figure 13

(a) For \((\mu _{1},\mu _{2})=(0.28,0.238999)\) between the curves \(H^{+}\) and \(T^{+}\), there are two limit cycles. The outer one is stable and the inner one is unstable. (b) For \((\mu _{1},\mu _{2})=(0.2813,0.237)\) below the curve \(H^{+}\), there is only a stable cycle. (c) For \((\mu _{1},\mu _{2})=(0.2819,0.23969)\) above the curve \(T^{+}\), there is no limit cycle. (d) For \((\mu _{1},\mu _{2})=(0.1593,0.1445)\) between the wedge of \(SN_{c}\), three equilibria \(E_{1}, E_{2}\) and \(E_{3}\) are a spiral source, a nodal source and a saddle, respectively