KATSYV, S.; KUKHARCHUK, V.; KONDRATENKO, N.; KUCHERUK, V.; KULAKOV, P.; KARABEKOVA, D. Development of the fuzzy sets theory: weak operations and extension principles. Bulletin of the Karaganda University. Mathematics Series, [S. l.], v. 111, n. 3, p. 59–71, 2023. DOI: 10.31489/2023m3/59-71. Disponível em: https://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/583. Acesso em: 4 sep. 2025.