Rabanovych, V.I. (2004) “On the Decomposition of an Operator into a Sum of Four Idempotents”, Ukrains’kyi Matematychnyi Zhurnal, 56(3), pp. 419–424. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/3764 (Accessed: 14 April 2025).