Lasuriya, R. A., & Stepanets, O. I. (2007). Multiple Fourier sums and ψ-strong means of their deviations on the classes of ψ-differentiable functions of many variables. Ukrains’kyi Matematychnyi Zhurnal, 59(8), 1075–1093. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/3371