Columbia subject headings:
Harvard subject headings:
Empresses--Holy Roman Empire--History.
Holy Roman Empire--History--843-1273.
Holy Roman Empire--Kings and rulers.
Princeton subject headings:
Empresses--Holy Roman Empire--Biography.
Holy Roman Empire--History--Franconian House, 1024-1125.
Holy Roman Empire--History--Saxon House, 919-1024.
Holy Roman Empire--Kings and rulers.