LEVIN, B. Ya.; MIROCHNIK, L. Ya. Estimation of the solutions of the Sturm-Liouville equation. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 46, n. 3, p. 244–278, 1994. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5760. Acesso em: 5 dec. 2025.