Columbia subject headings:
Islamic Empire--History--622-661.
Islamic Empire--History--661-750.
Islamic Empire--Politics and government.
Harvard subject headings:
Islamic Empire--History--622-661.
Islamic Empire--History--661-750.
Islamic Empire--Politics and government.
Princeton subject headings:
Islamic Empire--History--622-661.
Islamic Empire--History--661-750.
Islamic Empire--Politics and government.