“The Perturbation of the Interface of the Two-dimensional Diffraction Problem and an Approximating Muskat Modal”, J. Part. Diff. Eq., vol. 3, no. 2, pp. 85–96, Mar. 1990, Accessed: Dec. 05, 2025. [Online]. Available: https://global-sci.com/index.php/jpde/article/view/3662