Columbia subject headings:
Harvard subject headings:
Catholic Church--History--20th century--Congresses.
Communism and Christianity--Catholic Church--Congresses.
Fascism and the Catholic Church--Congresses.
National socialism and religion--Congresses.
Totalitarianism--Congresses
Princeton subject headings:
Church and state--Catholic Church--Congresses.
Church and state--Europe--History--20th century--Congresses.
Totalitarianism--History--20th century--Congresses.