Y. A. Mitropolskiy, G. P. Khoma, and . P. V. Tsynalko, “A periodic problem for the inhomogeneous equation of string oscillations”, Ukr. Mat. Zhurn., vol. 49, no. 4, pp. 558–565, Apr. 1997, Accessed: Apr. 13, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/5031