Badillo-Feliciano, J., and M. A. Lugo-López. 1976. “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 (4):597-605. https://doi.org/10.46429/jaupr.v60i4.10504.