1. Ethiopian perception on environmental protection and management cooperation in the Nile Basin;Abate,1990
2. AHDEL (American Heritage Dictionary of the English Language), 2000. 4th ed., Houghton Mifflin, Boston.
3. Brief description of a comprehensive three-dimensional process-response model of landform development;Ahnert;Z. Geomorphology N.F., Suppl.,1976
4. Slope instability assessment in the Blue Nile gorge, Ethiopia;Almaz,1998
5. Slope form and geomorphological processes; an Australian example;Arnett,1971