GORBACHUK, V. I.; GORBACHUK, M. L. Behavior of the extended spectral measure of a self-adjoint operator at infinity. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 49, n. 4, p. 510–516, 1997. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5024. Acesso em: 7 apr. 2025.