HANS, R. J. Maximal Covering Sets-I. The Journal of the Indian Mathematical Society, [S. l.], v. 35, n. 1-4, p. 171–179, 1971. DOI: 10.18311/jims/1971/16728. Disponível em: https://www.informaticsjournals.com/index.php/jims/article/view/16728. Acesso em: 1 may. 2024.