Pérez Escolar, Raúl, and César Ortiz Lugo. “Vertical Topsoiling, A Practicable Technique to Manage Soils With Markedly Compact Subsoils”. The Journal of Agriculture of the University of Puerto Rico, vol. 57, no. 3, July 1973, pp. 186-95, doi:10.46429/jaupr.v57i3.10742.