ARIOLI, G.; SZULKIN, A. Homoclinics solutions for a class of systems of second order differential equations. Topological Methods in Nonlinear Analysis, [S. l.], v. 6, n. 1, p. 189–197, 1995. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.1995.040. Acesso em: 9 jun. 2023.