Li J B. Hilbert’s 16-th problem and bifurcations of plannar polynomial vector fields[J]. Int J Bifur Chao,2003,13(1):47-106.
[2]
Dumorter F, Roussarie R, J Sotomayor. Generic 3-parameter families of vector fields on the plane, unfolding a singularity with nilpotent linear part: The cusp case of codimension 3[J]. Ergodic Theory and Dynamical Systems,1987,7(3):375-413.
[3]
Dumorter F, Li C Z, Zhang Z F. Unfolding of a quadratic integrable system with two centers and two undounded heteroclinic loops[J]. J Diff Eqns,1997,136:146-193.
[4]
Cheng S H, Feng J W. Bifurcation in perturbed Hamiltonian system with two centers[J]. J Math,1996,16(3):307-311.
[5]
Atabaigi A, Nyamoradi N, Zangeneh H R Z. The number of limit cycles of a quintic polynomial system[J]. Comput Math Appl,2009,57:677-684.
[6]
Asheghi R, Zangeneh H R Z. Bifurcations of limit cycles from quintic Hamiltonian systems with an eye-figure loop[J]. Nonlinear Anal,2008,68:2957-2976.
[7]
Asheghi R, Zangeneh H R Z. Bifurcations of limit cycles from quintic Hamiltonian systems with an eye-figure loop(II)[J]. Nonlinear Anal,2008,69:4143-4162.
Song Y. The Poincare bifurcation of a class of quadratic systems[J]. Pure Appl Math,2004,20(3):291-294.
[10]
Tan X X, Feng E M, Shen B Q. Study on the Poincare bifurcation of quadratic system with two centers and two unbounded heteroclinic loops once again[J]. Acta Math Appl Sic,2004,27(2):300-309.
Asheghi R, Zangeneh H R Z. Bifurcations and distribution of limit cycles which appear from two nests of periodic orbits[J]. Nonlinear Anal,2010,73:2398-2409.
[15]
Wang J H, Xiao D M. On the number of limit cycles in small perturbations of a class of hyper-elliptic Hamiltonian systems with one nilpotent saddle[J]. J Diff Eqns,2011,250:2227-2243.
