DORONIN, V. G.; LIGUN, A. A. Exact constants in Jackson-type inequalities for $L_2$-approximation on an axis. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 61, n. 1, p. 92–98, 2009. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3004. Acesso em: 27 apr. 2025.