Katsyv, S., V. Kukharchuk, N. Kondratenko, V. Kucheruk, P. Kulakov, and D. Karabekova. “Development of the Fuzzy Sets Theory: Weak Operations and Extension Principles”. Bulletin of the Karaganda University. Mathematics Series 111, no. 3 (September 30, 2023): 59–71. Accessed September 4, 2025. https://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/583.