Yeshkeyev, A.R. “Companions of the Fragments in the Jonsson Enrichment”. Bulletin of the Karaganda University. Mathematics Series 85, no. 1 (March 30, 2017): 41–45. Accessed September 7, 2025. http://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/143.