B. T. Bilalov and T. R. Muradov, “On equivalent bases in Banach spaces”, Ukr. Mat. Zhurn., vol. 59, no. 4, pp. 551–554, Apr. 2007, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/3329