UGOLʹNIKOV, A. P.; BEKKER, M. B. The Helson-Szegö theorem for operator-valued weight. Methods of Functional Analysis and Topology, [S. l.], v. 10, n. 3, p. 11–16, 2004. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/248. Acesso em: 18 dec. 2025.