RomanyukA. S. “Estimates for Approximation Characteristics of the Besov Classes $B_ r^{p,θ}$ of Periodic Functions of Many Variables in the Space $L_q. I$”. Ukrains’kyi Matematychnyi Zhurnal 53, no. 9 (September 25, 2001): 1224-1231. Accessed November 22, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/4341.