Yeshkeyev, A. and Ulbrikht, O. (2015) “On lattice of existential formulas for fragment of Jonsson set”, Bulletin of the Karaganda University. Mathematics Series, 79(3), pp. 33–39. Available at: http://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/44 (Accessed: 7 September 2025).