Columbia subject headings:
Poland--History--1945-1980--Chronology.
Poland--History--1980-1989--Chronology.
Harvard subject headings:
Poland--History--1945-1980--Chronology.
Poland--History--1980---Chronology.
Poland--History--1980-1989--Chronology.
Princeton subject headings:
Poland--History--1945---Chronology.