β€œOn Conditions for the Finiteness of the Spectrum of a Second Order Differential Operator With Integral Boundary Conditions: ”. Journal of Mathematics Mechanics and Computer Science 124, no. 4 (January 2, 2025): 26–37. Accessed July 5, 2026. https://bm.kaznu.kz/index.php/kaznu/article/view/1521.