Columbia subject headings:
Feudalism--Europe--History.
Harvard subject headings:
Europe--Economic conditions--To 1492.
Europe--History--476-1492.
Europe--Social conditions--To 1492.
Kievan Rus--History.
Kievan Rus--Social conditions.
Soviet Union--History.
Soviet Union--Social conditions.
Princeton subject headings:
Europe--Economic conditions--To 1492.
Europe--History--476-1492.
Europe--Social conditions--To 1492.
Russia--History.
Russia--Social conditions.