DORONIN, V. G.; LIGUN, A. A.; SERDYUK, A. S.; SHYDLICH, A. L. 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/3005. Acesso em: 5 dec. 2025.