Romanyuk, A. S. “On Estimates of the Kolmogorov Widths of the Classes $B_{p,θ}^r$ in the Space $L_q$”. Ukrains’kyi Matematychnyi Zhurnal 53, no. 7 (July 25, 2001): 996–1001. Accessed December 5, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/4320.