O’REGAN, D.; PAPAGEORGIOU, N. S.; SMYRLIS, G. Neumann problems with double resonance. Topological Methods in Nonlinear Analysis, [S. l.], v. 39, n. 1, p. 151–173, 2012. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2012.009. Acesso em: 25 apr. 2024.