Rukasov, V. I., and S. O. Chaichenko. “Approximation by De La Vallée-Poussin Operators on the Classes of Functions Locally Summable on the Real Axis”. Ukrains’kyi Matematychnyi Zhurnal 62, no. 7 (July 25, 2010): 968–978. Accessed April 25, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/2929.