1. On the existence of 2π-periodic solutions of Duffing type equation x″(t)+g(x(t−τ)=p(t);Xiankai;Chinese Sci. Bull,1994
2. Periodic solutions of a nonlinear delay equations;Layton;J. Math. Anal. Appl,1980
3. On the existence of harmonic solution for the n-dimensional Liènard equation with delay;Xiankai;J. Sys. Sci. Math. Sci,1999
4. An abstract theorem at resonance and its applications;Ma;J. Different. Equat,1998
5. On the existence of periodic solutions of second-order differential equations with deviating arguments;Lu;Acta Math. Sin,2002