Gyan Das, S. K. Sahani, A. K. Thakur. “On the Relative Strength of Double Fourier Series and Its Allied Series”. Mathematical Statistician and Engineering Applications 70, no. 1 (January 31, 2021): 826–837. Accessed July 3, 2024. https://philstat.org/index.php/MSEA/article/view/2744.