MOROZ, V.; VIGNOLI, A.; ZABREĬKO, P. P. On the three critical points theorem. Topological Methods in Nonlinear Analysis, [S. l.], v. 11, n. 1, p. 103–113, 1998. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.1998.006. Acesso em: 20 jun. 2024.