V. R. Voitsekhivs'kyi, “Jackson-Type Inequalities in the Space $S^p$”, Ukr. Mat. Zhurn., vol. 55, no. 9, pp. 1167–1177, Sep. 2003, Accessed: Feb. 16, 2026. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/3990