V. P. Burskii and A. S. Zhedanov, “On Dirichlet problem for string equation, Poncelet problem, Pell-Abel equation, and some other related problems”, Ukr. Mat. Zhurn., vol. 58, no. 4, pp. 435–450, Apr. 2006, Accessed: Feb. 16, 2026. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/3466