Landrau, Jr., P., G. Samuels, S. Alers-Alers, and C. González-Molina. “The Influence of Fertilizers on Tobacco Yields”. The Journal of Agriculture of the University of Puerto Rico, vol. 43, no. 1, Jan. 1959, pp. 56-68, doi:10.46429/jaupr.v43i1.12544.