POURNAKI M R, RAZANI A. On the existence of periodic solutions for a class of generalized forced Liénard equations [J]. Applied Mathematics Letters, 2007(3):248-254.
GAINES R E, MAWHIN J L. Coincidence degree and nonlinear differential equation [M]. Beilin:Springer-Verlag, 1977.40-60.
[5]
WANG Wei-bing, LUO Zhi-guo. Positive periodic solutions of second-order differential equations [J]. Applied Mathematics Letters, 2007(3):266-271.
[6]
ZHU Yan-ling, LU Shi-ping. Periodic solutions for p-Laplacian neutral functional differential equation with multiple deviating arguments [J]. Journal of Mathematical Analysis and Applications, 2007(2):1357-1367.doi:10.1016/j.jmaa.2007.02.085.
[7]
DING Wei, HAN Mao-an, YAN Ju-rang. Periodic boundary value problems for the second order functional differential equations [J]. Journal of Mathematical Analysis and Applications, 2004(1):341-351.doi:10.1016/j.jmaa.2004.05.019.
[8]
Li Yong-xiang. Positive periodic solutions of first and second order ordinary differential equations [J]. Chinese Ann Math (B), 2004(3):413-420.doi:10.1142/S025295990400038X.
[9]
LIU Bing-wen, HUANG Li-hong. Periodic solutions for a kind of Rayleigh equation with a deviating argument [J]. Journal of Mathematical Analysis and Applications, 2006(2):491-500.doi:10.1016/j.jmaa.2005.08.070.
