Ortega-Achury, Sandra L., et al. “Nutrient Concentrations in Runoff from Different Manure Amended Fields of the Tropics under Natural Rainfall Conditions”. The Journal of Agriculture of the University of Puerto Rico, vol. 91, no. 3-4, Oct. 2007, pp. 101-15, doi:10.46429/jaupr.v91i3-4.3279.