MARKIN, M. V. On a characterization of the generators of analytic semigroups in the cass of normal operators. Methods of Functional Analysis and Topology, [S. l.], v. 2, n. 2, p. 86–93, 1996. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/15. Acesso em: 19 dec. 2025.