V. P. Burskii and E. V. Kirichenko, “On the dirichlet problem for an improperly elliptic equation”, Ukr. Mat. Zhurn., vol. 63, no. 2, pp. 156–164, Feb. 2011, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/2707