Landrau, Jr., Pablo, Juan Pastor Rodríguez, George Samuels, Severiano Alers Alers, and R. Gandía Caro. “Effect of Spacing and Fertilization on the Yield of Potatoes”. The Journal of Agriculture of the University of Puerto Rico 39, no. 2 (April 1, 1955): 100–110. Accessed December 22, 2024. https://revistas.upr.edu/index.php/jaupr/article/view/12688.