| 1 | Chow S . Existence of periodic solutions of autonomous functional differential equations. J Differential Equations, 1974, 15: 350- 378 | | 2 | Hale J. Ordinary Differential Equations. Florida: Krieger Publishing Company, 1980 | | 3 | Chu J , Torres P . Applications of Schauder's fixed point theorem to singular differential equations. Bull Lond Math Soc, 2007, 39: 653- 660 | | 4 | Gaines R, Mawhin J. Coincidence Degree and Nonlinear Differential Equation. Berlin: Springer-Verlag, 1977 | | 5 | Lu S , Yu X . Periodic solutions for second order differential equations with indefinite singularities. Adv Nonlinear Anal, 2020, 9: 994- 1007 | | 6 | Godoy J , Zamora M . Periodic solutions for a second-order differential equation with indefinite weak singularity. Proc Roy Soc Edinburgh Sect A, 2019, 149: 1135- 1152 | | 7 | 张芷芬, 丁同仁, 黄文灶, 董镇喜. 微分方程定性理论. 北京: 科学出版社, 1985 | | 7 | Zhang Z , Ding T , Huang W , Dong Z . Qualitative Theory of Differential Equation. Beijing: Science Press, 1985 | | 8 | Kuznetsov Y. Elements of Applied Bifurcation Theory. New York: Springer-Verlag, 1995 | | 9 | Castelli R , Garrione M . Some unexpected results on the Brillouin singular equation: Fold bifurcation of periodic solutions. J Differential Equations, 2018, 265: 2502- 2543 | | 10 | Li J , Christie J , Gopalsamy K . Perturbed generalised Hamiltonian systems and some advection models. Bull Austral Math Soc, 1998, 57: 1- 24 | | 11 | Battelli F , Fe?kan M . On the Poincaré-Adronov-Melnikov method for the existence of grazing impact periodic solutions of differential equations. J Differential Equations, 2020, 268: 3725- 3748 | | 12 | Hakl R , Zamora M . Periodic solutions to second-order indefinite singular equations. J Differential Equations, 2017, 263: 451- 469 | | 13 | Nunez D , Perdomo O , Rivera A . On the stability of periodic solutions with defined sign in MEMS via lower and upper solutions. Nonlinear Anal: Real World Appl, 2019, 46: 195- 218 | | 14 | Lasota A , Opial Z . Sur les solutions périodiques deséquations différentielles ordinaires. Ann Polon Math, 1964, 16: 69- 94 | | 15 | Fonda A , Mawhin J . Quadratic forms, weighted eigenfunctions and boundary value problems for nonlinear second order ordinary differential equations. Proc Roy Soc Edinburgh Sect A, 1989, 112: 145- 153 | | 16 | Ortega R , Zhang M . Optimal bounds for bifurcation values of a superlinear periodic problem. Proc Roy Soc Edinburgh Sect A, 2005, 135: 119- 132 | | 17 | Li W , Zhang M . Non-degeneracy and uniqueness of periodic solutions for some superlinear beam equations. Appl Math Lett, 2009, 22: 314- 319 | | 18 | Torres P , Cheng Z , Ren J . Non-degeneracy and uniqueness of periodic solutions for $2n$-order differential equation. Discrete Contin Dyn Syst, 2013, 33: 2155- 2168 | | 19 | Zhang M . An abstract result on asymptotically positively homogeneous differential equations. J Math Anal Appl, 1997, 209: 291- 298 | | 20 | Ward J . Asymptotic conditions for periodic solutions of ordinary differential equations. Proc Amer Math Soc, 1981, 81: 415- 420 |
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