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 57, no. 3 (July 1, 1973): 186–195. Accessed April 26, 2024. https://revistas.upr.edu/index.php/jaupr/article/view/10742.