Samuels, G., F. González-Vélez, E. G. Boneta-García, and A. Sierra-Bracero. “Influence of Potash Fertilizers on Tobacco Yields and Quality on a Mabí Clay”. The Journal of Agriculture of the University of Puerto Rico 46, no. 3 (July 1, 1962): 183–188. Accessed December 9, 2022. https://revistas.upr.edu/index.php/jaupr/article/view/12333.