PichugovS. A. “Asymptotic Behavior of the Best Approximations for the Functions in $L_p$”. Ukrains’kyi Matematychnyi Zhurnal 45, no. 6 (June 25, 1993): 867–870. Accessed November 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/5876.