Samuels, George, and Héctor Gandía-Díaz. “Influence of Various Phosphate Fertilizers on Yields of Red Spanish Pineapples in Puerto Rico”. The Journal of Agriculture of the University of Puerto Rico 47, no. 4 (October 1, 1963): 242–245. Accessed December 22, 2024. https://revistas.upr.edu/index.php/jaupr/article/view/12960.