Stasyuk, S. A., and O. V. Fedunyk. “Approximation Characteristics of the Classes $B_{p,θ}^{Ω}$ of Periodic Functions of Many Variables”. Ukrains’kyi Matematychnyi Zhurnal 58, no. 5 (May 25, 2006): 692–704. Accessed April 28, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3486.