This paper discusses the existence of infinitely many periodic solutions for a semilinear fourth-order impulsive differential inclusion with a perturbed nonlinearity and two parameters. The approach is based on a critical point theorem for nonsmooth functionals.
Massimiliano Ferrara. Giuseppe Caristi. Amjad Salari. "Existence of Infinitely Many Periodic Solutions for Perturbed Semilinear Fourth-Order Impulsive Differential Inclusions." Abstr. Appl. Anal. 2016 1 - 12, 2016. https://doi.org/10.1155/2016/5784273