Columbia subject headings:
Crimes against humanity--History--20th century.
Genocide--History--20th century.
History, Modern--20th century.
Harvard subject headings:
Crimes against humanity--History--20th century.
Genocide--History--20th century.
History, Modern--20th century
Princeton subject headings:
Crimes against humanity--History--20th century.
Genocide--History--20th century.
History, Modern--20th century.