Olea Hernández, Héctor A. “The Participation of Mexican Undocumented Immigrants in the United States: A Tobit Model of Simultaneous Equations”. Estudios Económicos de El Colegio de México 5, no. 1 (January 1, 1990): 83–123. Accessed May 19, 2024. https://estudioseconomicos.colmex.mx/index.php/economicos/article/view/332.