. P. V. Tsynalko, “On a smooth solution of a boundary-value problem”, Ukr. Mat. Zhurn., vol. 50, no. 9, pp. 1293–1296, Sep. 1998, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/4849