MIKHAILETS, V. A.; GORIUNOV, A. Regularization of singular Sturm-Liouville equations. Methods of Functional Analysis and Topology, [S. l.], v. 16, n. 2, p. 120–130, 2010. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/445. Acesso em: 16 dec. 2025.