Columbia subject headings:
Social classes--Czechoslovakia--History--Congresses.
Social classes--Poland--History--Congresses.
Social structure--Czechoslovakia--History--Congresses.
Social structure--Poland--History--Congresses.
Harvard subject headings:
Social classes--Czechoslovakia--History--Congresses.
Social classes--Poland--History--Congresses.
Social structure--Czechoslovakia--History--Congresses.
Social structure--Poland--History--Congresses.
Princeton subject headings: