Solich, K. V. “Kolmogorov Widths of the Classes $B^{\Omega}_{p, \theta}$ of Periodic Functions of Many Variables in the Space $L_q$”. Ukrains’kyi Matematychnyi Zhurnal 64, no. 10 (October 25, 2012): 1416-1425. Accessed April 20, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/2668.