BABENKO, V. F.; KONAREVA, S. V. Jackson – Stechkin-type inequalities for the approximation of elements of Hilbert spaces. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 70, n. 9, p. 1155–1165, 2018. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/1626. Acesso em: 5 dec. 2025.