MIKHAILETS, V. A.; MOLYBOGA, V. M. Singular eigenvalue problems on the circle. Methods of Functional Analysis and Topology, [S. l.], v. 10, n. 3, p. 44–53, 2004. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/252. Acesso em: 18 dec. 2025.