Positive Solutions for Systems of Three-Point Nonlinear Boundary Value Problems on Time Scales. Global Journal of Science Frontier Research, [S. l.], v. 12, n. F12, p. 21–34, 2012. Disponível em: https://www.journalofscience.org/index.php/GJSFR/article/view/671. Acesso em: 13 aug. 2026.