Columbia subject headings:
Islamic Empire--History, Military.
Islamic Empire--History--622-661.
Islamic Empire--History--661-750.
Harvard subject headings:
Islamic Empire--History, Military.
Islamic Empire--History--622-661.
Islamic Empire--History--661-750--History.
Princeton subject headings:
Islamic Empire--History, Military.
Islamic Empire--History--622-661.
Islamic Empire--History--661-750--History.