Draganov, B. R. (2013) “An Improved Jackson Inequality for the Best Trigonometric Approximation”, Ukrains’kyi Matematychnyi Zhurnal, 65(9), pp. 1219–1226. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/2502 (Accessed: 29March2024).