DORONIN , V. G.; LIGUN , A.A. Problem of amplification of the Jackson-type inequalities . Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 44, n. 4, p. 475–480, 1992. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/7888. Acesso em: 6 dec. 2025.