Słowik, R. “The Drazin Inverses of Infinite Triangular Matrices and Their Linear Preservers”. Ukrains’kyi Matematychnyi Zhurnal 70, no. 4 (April 25, 2018): 534–548. Accessed April 14, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/1574.