The Central Bilād Al-Sūdān : tradition and adaptation ; essays on the geography and economic and political history of the Sudanic belt ; proceedings of the third International Conference of the Institute of African and Asian Studies, Univiversity of Khartoum, held from 8 to 13 November 1977 - Hassan, Yusuf Fadl; Doornbos, Paul (Tamaddon, 1979)