Serdyuk, A. S. “Approximation of Poisson Integrals by De La Vallée Poussin Sums”. Ukrains’kyi Matematychnyi Zhurnal 56, no. 1 (January 25, 2004): 97-107. Accessed May 19, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3731.