Gordón, R., J. Franco, and A. González. “DETERMINATION OF THE ECONOMIC AND PHYSIC OPTIMAL NITROGEN RATES FOR THE CORN CROP WITH THREE RESPONSE MODEL, AZUERO, PANAMA, 2000-2002.”. Ciencia Agropecuaria, no. 15, Feb. 2004, pp. 1-16, http://200.46.165.126/index.php/ciencia-agropecuaria/article/view/208.