KHAN, Waqar; HILA, Kostaq; CHEN, Guiyun. SANDWICH SETS AND CONGRUENCES IN COMPLETELY INVERSE \(AG^{∗∗}\)-GROUPOIDS. Italian Journal of Pure and Applied Mathematics, [S. l.], v. 39, p. 822–838, 2018. Disponível em: https://journals.uniurb.it/index.php/ijpam/article/view/6842. Acesso em: 26 sep. 2026.