Andrienko, V. A. (1999) “On the almost-everywhere convergence of the Riesz means of double orthogonal series”, Ukrains’kyi Matematychnyi Zhurnal, 51(7), pp. 867–880. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/4676 (Accessed: 12May2024).