VLASENKO, M. A.; POPOVA, N. D. On configurations of subspaces of a Hilbert space with fixed angles between them. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 56, n. 5, p. 606–615, 2004. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3781. Acesso em: 27 apr. 2025.