Even periodic solutions of higher order duffing differential equations

The existence of periodic solutions of higher order nonlinear periodic difference equations

“…In the recent years, the powerful and effective method of the coincidence degree has been applied to study the existence of periodic solutions in periodic equations and some good results have been obtained. By using Mawhin's continuation theorem, in , the existence of even solutions with minimum positive period for a class of higher order nonlinear Duffing differential equations was studied; the author in studied the existence of periodic solutions of a class of higher order delay differential equations; in , the authors studied the existence of positive periodic solutions of the following difference equation …”

Periodic solutions of second-order differential equations with multiple delays

“…Recently, some researchers [27][28][29][30][31] have begun to study the existence of solutions for second-order differential delay equation by using a variational method. However, to the best of authors' knowledge, the study of Kaplan-Yorke type periodic solutions of second-order differential delay equation using a variational method has received considerably less attention.…”

“…Motivated by the study in [7][8][9][10][11][12][13][14][15][16][21][22][23][24][27][28][29][30][31][32], in this article we are concerned with the existence of Kaplan-Yorke type periodic solutions of the following second-order differential delay equations…”