African Civilizations: Precolonial Cities and States in Tropical Africa

http://books.google.co.uk/books?hl=en&lr=&id=TV-0AaV_4EsC&oi=fnd&pg=PP12&dq=ancient+african+civilization&ots=zlscqiJ4uV&sig=LTX87Fs4kIXCNk8wTtg7ivitBdE#PPA66,M1