NovikovO. A., & RukasovV. I. (1995). Approximation of classes of continuous functions by generalized de la Vallée-Poussin sums. Ukrains’kyi Matematychnyi Zhurnal, 47(8), 1069–1079. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/5503