Abruña, F., J. Vicente-Chandler, and J. A. Rodríguez García. “Crop Response to Soil Acidity Factors in Ultisols and Oxisols in Puerto Rico. VIII. Yams”. The Journal of Agriculture of the University of Puerto Rico, vol. 67, no. 4, Oct. 1983, pp. 438-45, doi:10.46429/jaupr.v67i4.7738.