ISKAKOV, R. S.; PAVLENKO, V. N. Continuous approximations of discontinuous nonlinearities of semilinear elliptic-type equations. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 51, n. 2, p. 224–233, 1999. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4601. Acesso em: 14 apr. 2025.