MARANO, Salvatore A.; MOTREANU, Dumitru. A deformation theorem and some critical point results for non-differentiable functions. Topological Methods in Nonlinear Analysis, [S. l.], v. 22, n. 1, p. 139–158, 2003. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2003.032. Acesso em: 7 jul. 2025.