Godіch V. I. On invariant subspaces of completely continuous bisymmetrical operators . Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 18, n. 3, p. 103–107, 1966. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/8742. Acesso em: 14 apr. 2025.