Lugo-Mercado, Héctor M., et al. “Yield Response of Vegetables to Tillage Techniques on a Vertisol of the Semiarid Region of Puerto Rico”. The Journal of Agriculture of the University of Puerto Rico, vol. 72, no. 1, Jan. 1988, pp. 119-25, doi:10.46429/jaupr.v72i1.6841.