Wood et al, 2000, Analysis of Global Ecosystems: Agroecosystems, World
Resources Institute, Washington, D.C.
Oldeman, L. R., Hakkeling, R. T. A. and W. G. Sombroek. October 1990.
"World Map of the Status of Human-Induced Soil Degradation; Explanatory
Note". (The) Global Assessment of Soil Degradation, ISRIC and UNEP in
cooperation with the
... Winand Staring Centre, ISSS, FAO and ITC; 27 pages.
Deichmann, Uwe and Lars Eklundh. July 1991. "Global digital data sets for
land degradation studies: a GIS approach". GRID Case Study Series No. 4;
UNEP/GEMS & GRID; Nairobi, Kenya; 103 pages (mostly pp. 29-32). An
additional reference is UNEP's 1992 World Atlas of Desertification
(Edward Arnold, London, UK, 69 pages - see pages vii to ix).
United Nations Environmental Program, 1992, World Atlas of Desertification,
UNEP/GEMS and GRID, Nairobi, Kenya.