Pérez Escolar, Raul, and M. A. Lugo López. “Nature of Aggregation in Two Tropical Soils of Puerto Rico”. The Journal of Agriculture of the University of Puerto Rico 52, no. 3 (July 1, 1968): 227–232. Accessed April 20, 2024. https://revistas.upr.edu/index.php/jaupr/article/view/11509.