Bodraya, V. I., O. A. Novikov, and V. I. Rukasov. “Approximation of Classes of ψ-Integrals of Periodic Functions of Many Variables by Rectangular Linear Means of Their Fourier Series”. Ukrains’kyi Matematychnyi Zhurnal 57, no. 4 (April 25, 2005): 564–570. Accessed March 29, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3622.