Kanguzhin, B. E., and D. B. Nurakhmetov. “Correct Boundary Value Problems for 2-Order in Nonhomogeneous Differential Equation With Variable Coefficients”. Journal of Mathematics, Mechanics and Computer Science 64, no. 1 (February 12, 2019): 9–26. Accessed December 22, 2024. https://bm.kaznu.kz/index.php/kaznu/article/view/590.