Die Griechischen Philosophen in der Arabischen Überlieferung ("The Greek philosophers in the Arab tradition", 1873).
Der Islam im Morgen- und Abendland (“Islam in the west and the orient”; 1885–87).
Hebräische Schulgrammatik (“Hebrew school grammar”; 1878), the syntax of which was translated into English by James Robertson.
Reedition (1876),
Caspari's Arabische Grammatik, which he considerably enlarged.
Delectus Veterum Carminum Arabicorum (1890, with
Nöldeke), furnished with copious annotations, and thus rendered useful to those who desire to become acquainted with
Arabic poetry.
Edition (1884) of
Ibn Useibia's History of Physicians, with Arabic text and a critical commentary
online.
Several of his essays are contained in the "Zeitschrift der deutschen morgenländischen Gesellschaft" and "Beiträge zur Kunde der indogermanischen Sprachen". In 1887, he was appointed editor of the Orientalische Bibliographie.[3]