Columbia subject headings:
Abbasids.
Caliphs.
Islamic Empire--History.
Islamic Empire--Kings and rulers.
Islamic civilization.
Harvard subject headings:
Abbasids.
Caliphs.
Islamic Empire--Court and courtiers.
Islamic Empire--History.
Islamic Empire--Kings and rulers.
Islamic Empire--Social life and customs.
Islamic civilization
Princeton subject headings:
Caliphs.
Islamic Empire--Court and courtiers.
Islamic Empire--History.
Islamic Empire--Social life and customs.