Zhang, Zhifen; Li, Chengzhi On the number of limit cycles of a class of quadratic Hamiltonian systems under quadratic perturbations. (English) Zbl 0948.34020 Adv. Math., Beijing 26, No. 5, 445-460 (1997). Reviewer: Dmitry Turaev (Berlin) MSC: 34C07 37G15 34C23 PDFBibTeX XMLCite \textit{Z. Zhang} and \textit{C. Li}, Adv. Math., Beijing 26, No. 5, 445--460 (1997; Zbl 0948.34020)
Chow, Shiu-Nee; Li, Chengzhi; Wang, Duo A simple proof of the uniqueness of periodic orbits in the 1:3 resonance problem. (English) Zbl 0691.58028 Proc. Am. Math. Soc. 105, No. 4, 1025-1032 (1989). Reviewer: K.Chang MSC: 37G99 34C05 PDFBibTeX XMLCite \textit{S.-N. Chow} et al., Proc. Am. Math. Soc. 105, No. 4, 1025--1032 (1989; Zbl 0691.58028) Full Text: DOI