Sukhorolskyi, M. A. “On the Order of Local Approximation of Functions by Trigonometric Polynomials That Are Partial Sums of Averaging Operators”. Ukrains’kyi Matematychnyi Zhurnal 49, no. 5 (May 25, 1997): 706–714. Accessed May 18, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/5052.