Columbia subject headings:
Harvard subject headings:
Atheism--History--20th century.
Communism and Christianity--History--20th century.
Communism--History--20th century
National socialism and religion--History.
Princeton subject headings:
Atheism--History--20th century.
Communism and Christianity--History--20th century.
Communism--History--20th century.
National socialism and religion--History.