Romanyuk, V. S. “Approximation of Classes of Analytic Functions by Algebraic Polynomials and Kolmogorov Widths”. Ukrains’kyi Matematychnyi Zhurnal 48, no. 2 (February 25, 1996): 236–250. Accessed April 7, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/5351.