Figarella, Jacinto, Fernando Abruña, and José Vicente-Chandler. “Effect of Five Nitrogen Sources Applied at Four Rates to Pangola Grass Sod Under Humid Tropical Conditions”. The Journal of Agriculture of the University of Puerto Rico 56, no. 4 (October 1, 1972): 410-416. Accessed November 26, 2021. https://revistas.upr.edu/index.php/jaupr/article/view/10803.