The existence and multiplicity of positive periodic solutions for second-order non-autonomous singular dynamical systems are established with superlinearity or sublinearity assumptions at infinity for an appropriately chosen parameter. Our results provide a unified treatment for the problem and significantly improve several results in the literature. The proof of our results is based on the Krasnoselskii fixed point theorem in a cone. © 2010 Elsevier Inc.
Wang, H. (2010). Positive periodic solutions of singular systems with a parameter. Journal of Differential Equations, 249(12), 2986–3002. https://doi.org/10.1016/j.jde.2010.08.027