Kotova, O. V., and R. M. Trigub. “Exact Order of Approximation of Periodic Functions by One Nonclassical Method of Summation of Fourier Series”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 64, no. 7, July 2012, pp. 954-69, https://umj.imath.kiev.ua/index.php/umj/article/view/2631.