- African Economic History: Internal Development and External Dependency
- Trans-Saharan Africa in World History
- Middlemen of the Cameroon Rivers: The Duala and their Hinterland c.
- Sahara. Tausend Jahre Austausch von Ideen und Waren
- The Spiritual Use Of An Orchard Or Garden Of Fruit Trees: Set Forth In Divers Similitudes Betweene Natural And Spiritual Fruit Trees, According To Scripture And Experience...








