Ruiz, Isabel. “About the Theory and Empirical Analysis of ‘the Persistence of profit’and Its Applicability to Colombia”. Ecos de Economía 7, no. 16 (March 15, 2003): 65–76. Accessed May 13, 2024. https://publicaciones.eafit.edu.co/index.php/ecos-economia/article/view/2000.