SADYBEKOV, M. A.; IMANBAEV, N. S. Characteristic Determinant of a Boundary Value Problem, Which Does Not Have the Basis Property. Eurasian Mathematical Journal, [S. l.], v. 8, n. 2, p. 40–46, 2017. Disponível em: https://emj.enu.kz/index.php/main/article/view/662. Acesso em: 29 sep. 2025.