Villalobos-Cortés, A., B. Guerrero, J. Hassán, and D. Herrera. “FIXED EFFECTS OF PRODUCTIVE PERFORMANCE IN DOUBLE PURPOSE SYSTEM”. Ciencia Agropecuaria, no. 22, Mar. 2015, pp. 32-41, http://200.46.165.126/index.php/ciencia-agropecuaria/article/view/162.