GIRKO, V. L. Canonical spectral equation for empirical covariance matrices. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 47, n. 9, p. 1176–1189, 1995. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5517. Acesso em: 5 dec. 2025.