FedorenkoA. S. (2000) “Approximation of classes $C_\infty ^{\bar \psi }$ by zygmund sumsby zygmund sums”, Ukrains’kyi Matematychnyi Zhurnal, 52(6), pp. 856-860. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/4483 (Accessed: 22November2024).