Columbia subject headings:
Islamic Empire--Economic conditions.
Islamic Empire--History--661-750.
Syria--Economic conditions.
Syria--History--634-750.
Harvard subject headings:
Islamic Empire--Economic conditions.
Islamic Empire--History--661-750.
Syria--Economic conditions.
Syria--History--634-750.
Princeton subject headings:
Islamic Empire--Economic conditions.
Islamic Empire--History--661-750.
Syria--Economic conditions.
Syria--History--634-750.