AVERNA, D.; BONANNO, G. A three critical points theorem and its applications to the ordinary Dirichlet problem. Topological Methods in Nonlinear Analysis, [S. l.], v. 22, n. 1, p. 93–103, 2003. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2003.029. Acesso em: 22 jul. 2024.