Yusenko, A. A. “Quintuplets of Orthoprojectors Associated by a Linear Relation”. Ukrains’kyi Matematychnyi Zhurnal 61, no. 5 (May 25, 2009): 701-710. Accessed April 25, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3052.