Bonnet, J. A., Riera, A. R. and Roldán, J. (1958) “Yield Responses to Different N-P-K Levels, and Correlations With Foliar Analysis, in Sand-Culture Studies With Corn, Sugarcane, and Cotton”, The Journal of Agriculture of the University of Puerto Rico, 42(3), pp. 168–184. doi: 10.46429/jaupr.v42i3.13608.