SAMOILENKO, Yu. S.; YAKYMENKO, D. Yu. Scalar operators equal to the product of unitary roots of the identity operator. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 64, n. 6, p. 819–825, 2012. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/2619. Acesso em: 5 dec. 2025.