VAKARCHUK, S. B. Jackson-type inequalities with generalized modulus of continuity and exact values of the $n$-widths of the classes of $(ψ,β)$-differentiable functions in $L_2$. II. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 68, n. 8, p. 1021–1036, 2016. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/1899. Acesso em: 5 dec. 2025.