[1]
F. Z. Cong, Periodic solutions for 2kth with ordinary differential equations with non resonance, Nonlinear Anal. 32 (1997),787-793.
DOI: 10.1016/s0362-546x(97)00517-8
Google Scholar
[2]
F. Z. Cong, Q. D. Huang and S. Y. Shi, Existence and uniqueness of periodic solutions for (2n+1)th-order differential equations, J.Math. Anal. Appl. 241(2000), 1-9.
Google Scholar
[3]
W. Layton, Periodic solutions of nonlinear delay equations, J.Math. Anal. Appl. 77,(1980), 198-204.
Google Scholar
[4]
A. C. Lazer, Application of lemma on bilinear forms to a problem in nonlinear oscillations, Proceedings of the American Mathematical Society. 33 (1972), 89-94.
DOI: 10.1090/s0002-9939-1972-0293179-9
Google Scholar
[5]
W. Li, Periodic solutions for $2k$th order ordinary differential equation with resonance, J. Math. Anal. Appl. 259 (2001),157-167.
Google Scholar
[6]
Y. Li and H. Z. Wang, Periodic solutions of high order Duffing equations, Appl. Math. Chinese Univ. 6 (1991), 407-412.
Google Scholar
[7]
B. G. Liu and L. H. Huang, Periodic solutions for nonlinear n th order differential equations with delays, J. Math. Anal. Appl. 313 (2006), 700-716.
Google Scholar
[8]
R. Iannacci and M. N. Nkashama, On periodic solutions of forced second order differential equations with deviating arguments, Lecture Notes in Mathematical. 1151 (1984), Springer-Verlag, 224-232.
DOI: 10.1007/bfb0074731
Google Scholar
[9]
Krasnosel'skll. M. A., Topological methods in the theory of nonlinear integral equations, Macmillan Co., (1964), NewYork.
Google Scholar
[10]
S. Lu and W. Ge, Periodic solutions for a kind of Lie nard equations with deviating arguments, J. Math.Anal. Appl. 249 (2004), 213-243..
Google Scholar