SHABOZOV, M. Sh. Exact Jackson - Stechkin-type inequalities for 2π -periodic functions in L 2 and widths of some classes of functions. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 63, n. 10, p. 1434–1440, 2011. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/2816. Acesso em: 5 dec. 2025.