Pérez Escolar, R. and Lugo-López, M. A. (1968) “On the Possible Significance of High Free Iron Oxide Content in Mabí Clay, a Vertisol from East-Central Puerto Rico”, The Journal of Agriculture of the University of Puerto Rico, 52(1), pp. 47–52. doi: 10.46429/jaupr.v52i1.11722.