GRAEF, John R.; HEIDARKHANI, Shapour; KONG, Lingju. Infinitely many solutions for systems of multi-point boundary value problems using variational methods. Topological Methods in Nonlinear Analysis, [S. l.], v. 42, n. 1, p. 105–118, 2013. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2013.027. Acesso em: 8 apr. 2025.