A. S. Romanyuk, “On the best approximations and Kolmogorov widths of besov classes of periodic functions of many variables”, Ukr. Mat. Zhurn., vol. 47, no. 1, pp. 79–92, Jan. 1995, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/5385