RukasovV. I. and ChaichenkoS. O. (2001) “Approximation of $\overline \psi$-Integrals of Periodic Functions by de la Vallée-Poussin Sums (Low Smoothness)”, Ukrains’kyi Matematychnyi Zhurnal, 53(12), pp. 1641-1653. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/4384 (Accessed: 27July2024).