On the Frechet Differentiability of Free Boundary Operator for a Muskat Type Problem. Journal of Partial Differential Equations, [S. l.], v. 2, n. 1, p. 71–94, 1989. Disponível em: https://www.global-sci.com/index.php/jpde/article/view/3614. Acesso em: 27 feb. 2026.