Columbia subject headings:
Harvard subject headings:
Korea--History--Koryŏ period, 935-1392.
Korea--History--To 935.
Local government--Korea--History
Pugok
Serfdom--Korea--History.
Social classes--Korea--History
Social structure--Korea--History
Princeton subject headings:
Korea--Social conditions--935-1392.
Local government--Korea--History.
Pugok.
Social structure--Korea--History.