Theorem of Upper-lower Solutions for a Class of Nonlinear Degenerate Parabolic Systems Without Quasi-monotony. Journal of Partial Differential Equations, [S. l.], v. 2, n. 3, p. 62–78, 1989. Disponível em: https://gsp.tricubic.dev/jpde/article/view/3628. Acesso em: 15 mar. 2026.