Zhong, Chengkui; Wang, Aiyun; Lij, Xiulu Subharmonics of non-autonomous second order systems. (Chinese. English summary) Zbl 0865.34036 J. Lanzhou Univ., Nat. Sci. 30, No. 1, 17-24 (1994). Summary: We consider subharmonic solutions for a class of nonautonomous second-order systems. The main result is that, under some suitable assumptions, there exists a sequence of periodic solutions of the systems such that at most finitely many minimal periods ar equal. MSC: 34C25 Periodic solutions to ordinary differential equations 34C20 Transformation and reduction of ordinary differential equations and systems, normal forms Keywords:Legendre transformation; Sobolev inequality; periodic solutions PDFBibTeX XMLCite \textit{C. Zhong} et al., J. Lanzhou Univ., Nat. Sci. 30, No. 1, 17--24 (1994; Zbl 0865.34036)