1. Blum, W.E.H., 1990. The challenge of soil protection in Europe. In: World Resources Institute, 1991, Accounts Overdue. Oxford University Press, Oxford.
2. CEC, 1985. Soil Map of the European Communities, Scale 1:1000000, 7 Sheets and Explanatory Text. DG Agriculture CEC Publication, EUR 8982, Luxembourg.
3. CEC, 1992. CORINE Soil Erosion Risk and Important Land Resources in the Southern Regions of the European Community. DG Environment CEC Publication, EUR 13233 EN, Luxembourg.
4. De Barros, J., 1997. Quantitative analysis of selected land-use systems with sunflower. In: Bouma, J., De la Rosa, D., Driessen, P.M. (Promotors), Doctoral Thesis. Wageningen Agricultural University, Wageningen.
5. De la Rosa, D. (coord), 1996. MicroLEIS 4.1: Microcomputer-based Land Evaluation Information System. Integrated System for Land Datatransfer and Agro-ecological Land Evaluation. Software+Documentation. CSIC–IRNAS Publication, Sevilla, http://www.irnase.csic.es/microlei.htm.