Columbia subject headings:
Poland--Civilization--19th century--Congresses.
Poland--Civilization--20th century--Congresses.
Poland--Relations--Congresses.
Harvard subject headings:
Poland--Civilization--19th century--Congresses.
Poland--Civilization--20th century--Congresses.
Poland--Relations--Congresses.
Princeton subject headings:
Poland--Civilization--19th century--Congresses.
Poland--Civilization--20th century--Congresses.
Poland--Relations--Foreign countries--Congresses.