Motornaya, O. V. “On the Asymptotic Estimates of the Best Approximations of Differentiable Functions by Algebraić Polynomials in the Space $L_1$”. Ukrains’kyi Matematychnyi Zhurnal 45, no. 6 (June 25, 1993): 859–862. Accessed June 2, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/5874.