Columbia subject headings:
Harvard subject headings:
Caliphs.
Iran--History--640-1256--Early works to 1800.
Islam--History
Islamic Empire--History--622-661.
Muḥammad, Prophet, -632
Princeton subject headings:
Caliphs.
Iran--History--640-1256--Early works to 1800.
Islam--History.
Islamic Empire--History--622-661.
Muḥammad, Prophet, -632.