M. G. Kot, “Asymptotics of the eigenvalues of approximating differential equations with d-different coefficients”, Журнал Белорусского государственного университета. Математика. Информатика, no. 1, pp. 4–10, Dec. 2017, Accessed: Oct. 26, 2026. Available: https://journals.bsu.by/index.php/mathematics/article/view/730