MISHRA, S.; SATAPATHY, B.; RATH, N. Invariant Means and σ-Core. The Journal of the Indian Mathematical Society, [S. l.], v. 60, n. 1-4, p. 151–158, 1994. Disponível em: https://www.informaticsjournals.com/index.php/jims/article/view/21957. Acesso em: 29 apr. 2024.