Badillo-Feliciano, J., and M. A. Lugo-López. “Effect of Four Levels of N, P, K, and Micronutrients on Sweetpotato Yields in an Oxisol”. The Journal of Agriculture of the University of Puerto Rico 60, no. 4 (October 1, 1976): 597–605. Accessed March 28, 2024. https://revistas.upr.edu/index.php/jaupr/article/view/10504.