Iskakov RS, Pavlenko VN. Continuous approximations of discontinuous nonlinearities of semilinear elliptic-type equations. Ukr. Mat. Zhurn. [Internet]. 1999Feb.25 [cited 2024Nov.28];51(2):224–233. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/4601