Dougill, Andrew J.; Thomas, David S.G.; Heathwaite, A. Louise. Environmental Change in the Kalahari: Integrated Land Degradation Studies for Nonequilibrium Dryland Environments. Annals of the Association of American Geographers (Informa UK Limited). 1999, 89 (3): 420–442. ISSN 0004-5608. doi:10.1111/0004-5608.00156.