IBRAHIM, S. E.-S. On the Product of Self-Adjoint Sturm-Liouville Differential Operators in Direct Sum Spaces. Journal of Informatics and Mathematical Sciences, [S. l.], v. 4, n. 1, p. 93–109, 2012. DOI: 10.26713/jims.v4i1.71. Disponível em: http://www.rgnpublications.com/journals/index.php/jims/article/view/71. Acesso em: 2 may. 2024.