S. B. Vakarchuk, “Jackson-type inequalities and exact values of widths of classes of functions in the spaces $S^p , 1 ≤ p < ∞$”, Ukr. Mat. Zhurn., vol. 56, no. 5, pp. 595–605, May 2004, Accessed: Feb. 17, 2026. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/3780