Katsyv, S., Kukharchuk, V., Kondratenko, N., Kucheruk, V., Kulakov, P., & Karabekova, D. (2023). Development of the fuzzy sets theory: weak operations and extension principles. Bulletin of the Karaganda University. Mathematics Series, 111(3), 59–71. https://doi.org/10.31489/2023m3/59-71