HABETS, P.; OMARI, P. Existence and localization of solutions of second order elliptic problems using lower and upper solutions in the reversed order. Topological Methods in Nonlinear Analysis, [S. l.], v. 8, n. 1, p. 25–56, 1996. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.1996.020. Acesso em: 22 jul. 2024.