Fang, Fei; Wang, Nan; Liu, Shibo Multiple periodic solutions for nonlinear difference equations. (English) Zbl 1199.39029 J. Math. Study 41, No. 3, 234-239 (2008). MSC: 39A23 Periodic solutions of difference equations 39A10 Additive difference equations Keywords:multiple periodic solutions; Palais-Smale condition; three critical points theorem; Clark’s theorem; nonlinear difference equations PDFBibTeX XMLCite \textit{F. Fang} et al., J. Math. Study 41, No. 3, 234--239 (2008; Zbl 1199.39029)