Lugo-López, M. A., and Raúl Pérez-Escolar. “Attempts to Explain the Variability in the Cation-Exchange Capacity of Soils in Terms of Particle Size and Organic-Matter Levels”. The Journal of Agriculture of the University of Puerto Rico 53, no. 4 (October 1, 1969): 369–373. Accessed April 24, 2024. https://revistas.upr.edu/index.php/jaupr/article/view/11150.