HENDERSON, J.; NTOUYAS, S.K.; PURNARAS, I.K. Positive Solutions for Systems of Three-point Nonlinear Boundary Value Problems with Deviating Arguments. CUBO, A Mathematical Journal, [S. l.], v. 11, n. 3, p. 79–100, 2009. Disponível em: https://cubo.ufro.cl/index.php/cubo/article/view/1464. Acesso em: 7 mar. 2026.