PARFINOVYCH, N. V. Exact values of the best (α, β) -approximations of classes of convolutions with kernels that do not increase the number of sign changes. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 69, n. 8, p. 1073–1083, 2017. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/1759. Acesso em: 5 dec. 2025.