Bilalov, B. T., and T. R. Muradov. “On Equivalent Bases in Banach Spaces”. Ukrains’kyi Matematychnyi Zhurnal 59, no. 4 (April 25, 2007): 551–554. Accessed June 13, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3329.