MIKHAILETS, V. A.; MOLYBOGA, V. M. Uniform estimates for the semi-periodic eigenvalues of the singular differential operators. Methods of Functional Analysis and Topology, [S. l.], v. 10, n. 4, p. 30–57, 2004. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/257. Acesso em: 16 dec. 2025.