A. S. Serdyuk, “Approximation of Poisson integrals by de la Valleé-Poussin sums in uniform and integral metrics”, Ukr. Mat. Zhurn., vol. 62, no. 12, pp. 1672–1686, Dec. 2010, Accessed: Apr. 13, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/2991