Vakarchuk, S. B. “Jackson-Type Inequalities With Generalized Modulus of Continuity and Exact Values of the $n$-Widths of the Classes of $(ψ,β)$-Differential Functions in $L_2$. I”. Ukrains’kyi Matematychnyi Zhurnal 68, no. 6 (June 25, 2016): 723-745. Accessed April 19, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/1874.