Babenko V. F. “The Best Approximations of the Classes of Functions Preset by Means of the Continuity Modulus”. Ukrains’kyi Matematychnyi Zhurnal 44, no. 5 (May 26, 1992): 579-589. Accessed October 6, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/7952.