The existence results of positive ω-periodic solutions are obtained for the second-order functional differential equation with multiple delays , where is a positive ω-periodic function, is a continuous function which is ω-periodic in t, and are ω-periodic functions. The existence conditions concern the first eigenvalue of the associated linear periodic boundary problem. Our discussion is based on the fixed-point index theory in cones.
Qiang Li. Yongxiang Li. "On the Existence of Positive Periodic Solutions for Second-Order Functional Differential Equations with Multiple Delays." Abstr. Appl. Anal. 2012 (SI05) 1 - 13, 2012. https://doi.org/10.1155/2012/929870