RADZIEVSKII, G. V. Minimality of root vectors of operator functions analytic in an angle. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 46, n. 5, p. 545–566, 1994. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5718. Acesso em: 5 dec. 2025.