Tang, Chun-Lei; Wu, Xing-Ping A note on periodic solutions of nonautonomous second-order systems. (English) Zbl 1055.34084 Proc. Am. Math. Soc. 132, No. 5, 1295-1303 (2004). The authors study the multiplicity of periodic solutions for the second-order equation \[ \ddot u + \nabla F(t,u) = e(t),\quad u\in\mathbb R^n, \] where the function \(F\) is periodic in the first \(r\) components of \(u\) and subquadratically in the other \(n-r\) components. Using minimax methods, they show that there are at least \(r+1\) geometrically distinct periodic solutions. Reviewer: Bin Liu (Beijing) Cited in 11 Documents MSC: 34C25 Periodic solutions to ordinary differential equations Keywords:periodic solutions; nonautonomous second-order systems; minimax methods PDFBibTeX XMLCite \textit{C.-L. Tang} and \textit{X.-P. Wu}, Proc. Am. Math. Soc. 132, No. 5, 1295--1303 (2004; Zbl 1055.34084) Full Text: DOI