I. I. Skrypnik, “Limiting behavior of the solutions to linear second-order parabolic equations”, Ukr. Mat. Zhurn., vol. 45, no. 7, pp. 1029–1038, Jul. 1993, Accessed: Apr. 13, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/5896