RIBARSKA, Nadezhda; TSACHEV, Tsvetomir; KRASTANOV, Mikhail. The intrinsic mountain pass principle. Topological Methods in Nonlinear Analysis, [S. l.], v. 12, n. 2, p. 309–322, 1998. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.1998.044. Acesso em: 8 jul. 2025.