Samuels, G., E. G. Boneta-García, and F. González-Vélez. “A Comparison of Phosphate Fertilizers for Tobacco”. The Journal of Agriculture of the University of Puerto Rico 46, no. 1 (January 1, 1962): 48–54. Accessed December 22, 2024. https://revistas.upr.edu/index.php/jaupr/article/view/12293.