Bitimkhan, S. “Hardy-Littlewood Theorem for Series With General Monotone Coefficients”. Bulletin of the Karaganda University. Mathematics Series 90, no. 2 (June 30, 2018): 43–48. Accessed August 23, 2025. http://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/206.