Vakarchuk, B. S. “Jackson-Type Inequalities With Generalized Modulus of Continuity and Exact Values of the $n$-Widths for the Classes of $(ψ,β)$-Differentiable Functions in $L_2$. III”. Ukrains’kyi Matematychnyi Zhurnal 68, no. 10 (October 25, 2016): 1299-1319. Accessed March 28, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/1922.