SCHECHTER, M. Critical points when there is no saddle point geometry. Topological Methods in Nonlinear Analysis, [S. l.], v. 6, n. 2, p. 295–308, 1995. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.1995.047. Acesso em: 22 jul. 2024.