Grigoryan, M. G., and V. G. Krotov. “Quasiunconditional Basis Property of the Faber – Schauder System”. Ukrains’kyi Matematychnyi Zhurnal 71, no. 2 (February 25, 2019): 210-219. Accessed April 25, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/1432.