HATAMLEH, R.; ZOLOTAREV, V. A. Triangular models of commutative systems of linear operators close to unitary operators. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 68, n. 5, p. 694–711, 2016. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/1872. Acesso em: 27 apr. 2025.