[1]
R. S. Iskakov and V. N. Pavlenko, “Continuous approximations of discontinuous nonlinearities of semilinear elliptic-type equations”,
Ukr. Mat. Zhurn., vol. 51, no. 2, pp. 224–233, Feb. 1999, Accessed: Apr. 13, 2025. [Online]. Available:
https://umj.imath.kiev.ua/index.php/umj/article/view/4601