IMANBAEV, N.S. Characteristic determinant of the spectral problem for the Sturm-Liouville operator with the perturbed boundary value conditions. Bulletin of the Karaganda University. Mathematics Series, [S. l.], v. 82, n. 2, p. 68–73, 2016. Disponível em: http://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/105. Acesso em: 24 aug. 2025.