B. V. Bazalii and S. P. Degtyarev, “On one boundary-value problem for a strongly degenerate second-order elliptic equation in an angular domain”, Ukr. Mat. Zhurn., vol. 59, no. 7, pp. 867–883, Jul. 2007, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/3352