WANG, Chao, WANG, Zhiguo and LIU, Qihuai. Infinitely many small bouncing solutions of Hill’s type impact oscillators nearby the origin. Topological Methods in Nonlinear Analysis. Online. 1 October 2025. Vol. 66, no. 1, pp. 215 - 235. [Accessed 12 December 2025]. DOI 10.12775/TMNA.2025.008.