Delgado, R., Cabrera de Bisbal, E., Navarro, L. and Paredes, M. 2010. Accumulation of S, Ca, Mg, Fe, Zn and Mn and their relatioship with dry matter production in cowpea grown under minimum and conventional tillage in a Mollisol soil of Venezuela. Agronomía Tropical. 60, 2 (Mar. 2010), 162-170.