Yang, Congmin, and Zaihong Wang. “On the Existence of Periodic Solutions for Liénard Type $\phi$-Laplacian Equation”. Topological Methods in Nonlinear Analysis 62, no. 1 (September 23, 2023): 219–237. Accessed June 28, 2025. https://apcz.umk.pl/TMNA/article/view/46311.