Kotova, O. V., & Trigub, R. M. (2012). Exact order of approximation of periodic functions by one nonclassical method of summation of Fourier series. Ukrains’kyi Matematychnyi Zhurnal, 64(7), 954-969. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/2631