DUDKIN, M. Ye. Analog of the Krein Formula for Resolvents of Normal Extensions of a Prenormal Operator. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 54, n. 4, p. 555–562, 2002. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4092. Acesso em: 5 dec. 2025.