MOGHADDASI, Gholamreza; ZOLFAGHARI, Parvaneh. THE QUOTIENT ULTRA-GROUPS. Italian Journal of Pure and Applied Mathematics, [S. l.], v. 36, p. 211–218, 2016. Disponível em: https://journals.uniurb.it/index.php/ijpam/article/view/6635. Acesso em: 5 sep. 2026.