Murillo, J. M., F. Moreno, I. F. Girón, and M. I. Oblitas. “Conservation Tillage: Long Term Effect on Soil and Crops under Rainfed Conditions in South-West Spain (Western Andalusia)”. Spanish Journal of Agricultural Research, Vol. 2, no. 1, Mar. 2004, pp. 35-43, doi:10.5424/sjar/2004021-58.