Columbia subject headings:
Abbasids.
Caliphs--Islamic Empire--Biography.
Islamic Empire--History--750-1258.
Islamic Empire--Kings and rulers--Biography.
Harvard subject headings:
Abbasids.
Caliphs--Islamic Empire--Biography.
Islamic Empire--History--750-1258.
Islamic Empire--Kings and rulers--Biography.
Princeton subject headings:
Abbasids.
Caliphs--Islamic Empire--Biography.
Islamic Empire--History--750-1258.
Islamic Empire--Kings and rulers--Biography.