The Nonlinear Boundary Value Problems of Three Elements for the First Order Quasilinear Elliptic Systems. Journal of Partial Differential Equations, [S. l.], v. 5, n. 1, p. 90–96, 1992. Disponível em: https://global-sci.com/index.php/jpde/article/view/3706. Acesso em: 5 dec. 2025.