Columbia subject headings:
Catholic Church--Foreign relations.
Church and state--Catholic Church--History--20th century.
Communism and Christianity--Catholic Church--History--20th century.
Papacy--History--20th century.
Harvard subject headings:
Church and state--Catholic Church--History--20th century
Communism and Christianity--Catholic Church--History--20th century.
Papacy--History--20th century
Princeton subject headings:
Church and state--Catholic Church--History--20th century.
Communism and Christianity--Catholic Church--History--20th century.
Papacy--History--20th century.