PALYUTKIN, V. G. Distribution of eigenvalues of the Sturm-Liouville problem with slowly increasing potential. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 48, n. 6, p. 813–825, 1996. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5281. Acesso em: 27 apr. 2025.