Lugo-López, M. A., J. Badillo-Feliciano, and L. Calduch. “Performance of Oilseed Sunflower Cultivars in an Oxisol in Northwestern Puerto Rico”. The Journal of Agriculture of the University of Puerto Rico 61, no. 2 (April 1, 1977): 200–203. Accessed April 19, 2024. https://revistas.upr.edu/index.php/jaupr/article/view/10459.