GORBACHUK, M. L.; MOKROUSOV, Yu. G. On density of some sets of infinitely differentiable vectors of a closed operator on a Banach space. Methods of Functional Analysis and Topology, [S. l.], v. 8, n. 1, p. 23–29, 2002. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/173. Acesso em: 18 dec. 2025.