Columbia subject headings:
Catholic Church--Controversial literature--Catholic authors.
Christianity and politics--History--20th century.
Communism and Christianity--Catholic Church--History--20th century.
Harvard subject headings:
Catholic Church--Doctrines.
Christianity and politics--History--20th century
Communism and Christianity--Catholic Church--History--20th century.
Princeton subject headings:
Catholic Church--Doctrines--Catholic authors.
Christianity and politics--History--20th century.
Communism and Christianity--Catholic Church--History--20th century.