Khan, W., Hila, K. and Chen, G. (2018) “SANDWICH SETS AND CONGRUENCES IN COMPLETELY INVERSE \(AG^{∗∗}\)-GROUPOIDS”, Italian Journal of Pure and Applied Mathematics, 39, pp. 822–838. Available at: https://journals.uniurb.it/index.php/ijpam/article/view/6842 (Accessed: 26 September 2026).