González Parra, Gilberto, and Abraham J Arenas. “A Mathematical Model for Social Security Systems With Dynamical Systems”. Ingeniería y Ciencia 10, no. 19 (January 30, 2014): 33–53. Accessed November 22, 2024. https://publicaciones.eafit.edu.co/index.php/ingciencia/article/view/2034.