Yeshkeyev, A.R., O.I. Ulbrikht, and G.A. Urken. “Similarities of Jonsson spectra’s Classes”. Bulletin of the Karaganda University. Mathematics Series 112, no. 4 (December 29, 2023): 130–143. Accessed October 14, 2025. https://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/611.