Abruña, F., R. Pérez-Escolar, J. Vicente-Chandler, R. W. Pearson, and S. Silva. “Response of Corn to Acidity Factors in Eight Tropical Soils”. The Journal of Agriculture of the University of Puerto Rico, vol. 58, no. 1, Jan. 1974, pp. 59-77, doi:10.46429/jaupr.v58i1.10703.