DRAGANOV, B. R. An Improved Jackson Inequality for the Best Trigonometric Approximation. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 65, n. 9, p. 1219–1226, 2013. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/2502. Acesso em: 5 dec. 2025.