KoganA. M. “On the Best Approximation of Classes $W^r H^{ω}$ by Algebraic Polynomials in the Space $L_1$”. Ukrains’kyi Matematychnyi Zhurnal 51, no. 11 (November 25, 1999): 1456-1466. Accessed July 27, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/4747.