LE, V. K.; SCHMITT, K. Some general concepts of sub- and supersolutions for nonlinear elliptic problems. Topological Methods in Nonlinear Analysis, [S. l.], v. 28, n. 1, p. 87–103, 2006. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2006.021. Acesso em: 29 may. 2024.