Virto, I., M. J. Imaz, O. Fernández-Ugalde, I. Urrutia, A. Enrique, and P. Bescansa. “Soil Quality Evaluation Following the Implementation of Permanent Cover Crops in Semi-Arid Vineyards. Organic Matter, Physical and Biological Soil Properties”. Spanish Journal of Agricultural Research, Vol. 10, no. 4, Oct. 2012, pp. 1121-32, doi:10.5424/sjar/2012104-613-11.