Bonnet, J. A., P. Tirado Sulsona, and F. Abruña. “Effect of Lime-Phosphorus and Green Manure on Sweet Potatoes and Corn Grown in Acid Soils”. The Journal of Agriculture of the University of Puerto Rico 31, no. 4 (October 1, 1947): 303–321. Accessed December 22, 2024. https://revistas.upr.edu/index.php/jaupr/article/view/12857.