Alfred von Kremer: Geschichte der herrschenden Ideen des Islams. Leipzig, 1868.

Alfred von Kremer: Culturgeschichte des Orients unter den Chalifen. 2 vols. Wien, 1875-77. Culturgeschichtliche Streifzüge. Leipzig, 1873.

Edward G. Browne: A Year Among the Persians. London, 1893. A most valuable account of modern Persian life, philosophy, and theology, and especially of Sufiism and Babism.

Edward G. Browne: A Literary History of Persia. New York, 1902. Really political and religious prolegomena to such a history.

G. A. Herklots: Qanoon-e-Islam, or the Customs of the Moosulmans of India. London, 1832.

II
On Muslim History and on Present Condition of Muslim World

August Müller: Die Beherrscher der Gläubigen. Berlin, 1882. A very brightly written sketch based on thorough knowledge.

Gustav Weil: Geschichte der Chalifen. 3 vols. Mannheim, 1846-1851.

Sir William Muir: The Caliphate, its Rise, Decline and Fall. London, 1891.