V. I. Buslaev, “On a criterion of rationality for a series in orthogonal polynomials”, Ukr. Mat. Zhurn., vol. 62, no. 8, pp. 1139–1144, Aug. 2010, Accessed: Apr. 13, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/2943