YUSENKO, A. A. Quintuplets of orthoprojectors associated by a linear relation. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 61, n. 5, p. 701–710, 2009. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3052. Acesso em: 5 dec. 2025.