Yeshkeyev, A.R., and G.A. Urken. “The Admissibility and Similarity of Jonsson Theories”. Bulletin of the Karaganda University. Mathematics Series 89, no. 1 (March 30, 2018): 42–48. Accessed December 8, 2025. https://mts.buketov.edu.kz/mathematics-vestnik/article/view/212.