Josef van Ess, Emeritus Professor of Islamic Studies and Semitic Languages, University of Tübingen, Germany, has published widely on the Intellectual History of the Islamic World; Islamic theology and philosophy, especially with respect to the formative period (8th-10th centuries), the age of the Mongol conquests (13th-14th centuries) and Islamic mysticism. His most famous work is his Theologie und Gesellschaft im 2. und 3. Jahrhundert Hidschra published in 6 volumes (de Gruyter 1991-97), the English edition of which is now being published by Brill in 4 volumes.
Hinrich Biesterfeldt Retired Professor of Arabic and Islamic studies at the Department of Oriental and Islamic Studies of the Ruhr-Universität Bochum, has published widely on the transmission of Greek philosophy and medicine to Arabic culture. His other fields of research include the early history of classifications of knowledge in Islam and classical Arabic prose literature.