1. Oldeman LR, Hakkeling RTA, Sombroek W.G. Global Assessment of Human-induced Soil Degradation (GLASOD). World map of the status of human-induced soil degradation. Winand Staring Centre-ISSS-FAO-ITC (eds.) 1991. 41 pp.
2. Reports of the technical working groups established under the thematic strategy for soil protection. EUR 21319 EN/1;Van-Camp,2004