S. A. . Aldashev, “On some boundary value problems for linear multidimensional hyperbolic equations of the second order”, Ukr. Mat. Zhurn., vol. 43, no. 3, pp. 415–420, Feb. 1991, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/9624