We apply the Krasnoselskii fixed-point theorem to investigate the existence of multiple positive periodic solutions for a class of impulsive functional differential equations with a parameter; some verifiable sufficient results are established easily. In particular, our results extend and improve some previous results.
Zhenguo Luo. "Multiple Positive Periodic Solutions for Functional Differential Equations with Impulses and a Parameter." Abstr. Appl. Anal. 2014 (SI01) 1 - 13, 2014. https://doi.org/10.1155/2014/812867