SerdyukA. S. 2010. “Approximation of Poisson Integrals by De La Valleé-Poussin Sums in Uniform and Integral Metrics”. Ukrains’kyi Matematychnyi Zhurnal 62 (12), 1672–1686. https://umj.imath.kiev.ua/index.php/umj/article/view/2991.