HALL, M. A.; ESKIN, G. Ergoregions between two ergospheres. Methods of Functional Analysis and Topology, [S. l.], v. 24, n. 2, p. 98–106, 2018. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/688. Acesso em: 15 dec. 2025.