Columbia subject headings:
Emperors--Japan--History--To 1500.
Japan--Kings and rulers--Legal status, laws, etc.--History--To 1500.
Harvard subject headings:
Emperors--Japan--History--To 794.
Japan--Kings and rulers--Legal status, laws, etc.--History--To 794.
Princeton subject headings:
Emperors--Japan--History--To 794.
Japan--Kings and rulers--Legal status, laws, etc.--History--To 794.