Kadets, M. I. “On Absolute, Perfect, and Unconditional Convergences of Double Series in Banach Spaces”. Ukrains’kyi Matematychnyi Zhurnal 49, no. 8 (August 25, 1997): 1032–1041. August. Accessed May 19, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/5098.