CHABROWSKI, J. Elliptic variational problems with indefinite nonlinearities. Topological Methods in Nonlinear Analysis, [S. l.], v. 9, n. 2, p. 221–231, 1997. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.1997.010. Acesso em: 22 jul. 2024.