Changphas, Thawhat, and Bijan Davvaz. “BI-HYPERIDEALS AND QUASI-HYPERIDEALS IN ORDERED SEMIHYPERGROUPS”. Italian Journal of Pure and Applied Mathematics 35 (December 31, 2015): 493–508. Accessed August 16, 2026. https://journals.uniurb.it/index.php/ijpam/article/view/6404.