@article{Wang_Chu_Siegmund_2015, title={Periodic solutions for second order singular differential systems with parameters}, volume={46}, url={https://apcz.umk.pl/TMNA/article/view/TMNA.2015.058}, DOI={10.12775/TMNA.2015.058}, abstractNote={In this paper we consider the existence of periodic solutions of one-parameter and two-parameter families of second order singular differential equations.}, number={2}, journal={Topological Methods in Nonlinear Analysis}, author={Wang, Fanglei and Chu, Jifeng and Siegmund, Stefan}, year={2015}, month={Dec.}, pages={549–562} }