Li, Xiong; Zhang, Ziheng On the existence of positive periodic solutions of systems of second order differential equations. (English) Zbl 1225.34033 Math. Nachr. 284, No. 11-12, 1472-1482 (2011). MSC: 34B18 34B27 47H10 PDFBibTeX XMLCite \textit{X. Li} and \textit{Z. Zhang}, Math. Nachr. 284, No. 11--12, 1472--1482 (2011; Zbl 1225.34033) Full Text: DOI
Li, Xiong; Zhang, Ziheng Periodic solutions for second-order differential equations with a singular nonlinearity. (English) Zbl 1162.34316 Nonlinear Anal., Theory Methods Appl., Ser. A, Theory Methods 69, No. 11, 3866-3876 (2008). MSC: 34B18 34B16 34B27 47N20 PDFBibTeX XMLCite \textit{X. Li} and \textit{Z. Zhang}, Nonlinear Anal., Theory Methods Appl., Ser. A, Theory Methods 69, No. 11, 3866--3876 (2008; Zbl 1162.34316) Full Text: DOI