Rabinowitz, Paul H. “Homoclinics for an Almost Periodically Forced Singular Hamiltonian System”. Topological Methods in Nonlinear Analysis 6, no. 1 (September 1, 1995): 49–66. Accessed July 3, 2024. https://apcz.umk.pl/TMNA/article/view/TMNA.1995.031.