Ashyralyev, A., C. Ashyralyyev, and M. Sadybekov. “Functional Analysis in Interdisciplinary Applications”. Bulletin of the Karaganda University. Mathematics Series 120, no. 4 (December 30, 2025): 4. Accessed January 11, 2026. https://mts.buketov.edu.kz/mathematics-vestnik/article/view/1146.