O. I. Kuznetsovci, “Strong summability of multiple Fourier series and Sidon-type inequalities”, Ukr. Mat. Zhurn., vol. 50, no. 12, pp. 1630–1635, Dec. 1998, Accessed: Feb. 17, 2026. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/4782