Columbia subject headings:
Catholic Church--Europe, Central--History--20th century.
Catholic Church--Europe, Eastern--History--20th century.
Church and state--Europe, Central--History--20th century--Congresses.
Church and state--Europe, Eastern--History--20th century--Congresses.
Communism and Christianity--Catholic Church--History--20th century--Congresses.
Harvard subject headings:
Catholic Church--Europe, Central--History--20th century.
Catholic Church--Europe, Eastern--History--20th century.
Church and state--Europe, Central--History--20th century--Congresses.
Church and state--Europe, Eastern--History--20th century--Congresses.
Communism and Christianity--Catholic Church--History--20th century--Congresses.
Princeton subject headings: