S. A. Aldashev, “Many-dimensional Dirichlet and Tricomi problems for one class of hyperbolic-elliptic equations”, Ukr. Mat. Zhurn., vol. 49, no. 12, pp. 1587–1593, Dec. 1997, Accessed: Apr. 09, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/5162