1. Fragile ecosystems in Near East countries: problems and management;Kassas,1998
2. UNSO. Assessment of desertification and drought in the Sudano–Sahelian region. New York: United Nations Sudano–Sahelian Office, 1992.
3. Troll C. Wunstensteppen und nebeloasen im sudnubischen kustengebirge. Zeitschrift der Gesselschaft fur Erdkunde zu Berlin, 1935.
4. The mist oasis of Erkwit;Kassas;J. Ecol.,1956
5. Population, society and desertification;Kates,1977