N. G. Sorokina, “On the normal solvability of the Tricomi problem for an equation of the Lavrentyev — Bitsadze type”, Ukr. Mat. Zhurn., vol. 23, no. 1, pp. 34–42, Dec. 1970, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/8476