RukasovV. I. (2003) “Approximation of Continuous Functions by de la Vallée-Poussin Operators”, Ukrains’kyi Matematychnyi Zhurnal, 55(3), pp. 414-424. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/3915 (Accessed: 6October2024).