Abruña-Rodríguez, Fernando, and José Vicente-Chandler. “Organic-Matter Activity of Some Typical Soils of Puerto Rico”. The Journal of Agriculture of the University of Puerto Rico 39, no. 2 (April 1, 1955): 65–76. Accessed April 24, 2024. https://revistas.upr.edu/index.php/jaupr/article/view/12684.