Chumpungam, Dawan, and Sorasak Leeratanavalee. “Strongly Solid Varieties in Many-Sorted Algebras”. Communications in Mathematics and Applications 9, no. 4 (December 25, 2018): 677–688. Accessed June 16, 2025. http://www.journals.rgnpublications.com/index.php/cma/article/view/972.