Columbia subject headings:
Harvard subject headings:
Catholic Church--Foreign relations--Poland--Sources--Bibliography--Catalogs.
Catholic Church. Apostolic Nunciature (Poland)--Archives--Catalogs.
Pius XI, Pope, 1857-1939--Journeys--Poland--History--Sources--Bibliography--Catalogs.
Pius XI, Pope, 1857-1939--Travel--Poland--History--Sources--Bibliography--Catalogs.
Poland--Church history--20th century--Sources--Bibliography--Catalogs.
Poland--Foreign relations--Catholic Church--Sources--Bibliography--Catalogs.
Princeton subject headings:
Catholic Church--Foreign relations--Poland--20th century--Sources.
Pius XI, Pope, 1857-1939--Archives.
Poland--Church history--20th century--Sources.
Poland--Foreign relations--Catholic Church--20th century--Sources.