Columbia subject headings:
Austria--History--20th century--Sources.
Austria--History--20th century.
Charles I, Emperor of Austria, 1887-1922.
Harvard subject headings:
Austria--History--20th century--Sources.
Austria--History--20th century.
Charles I, Emperor of Austria, 1887-1922.
Europe, Central--History--20th century--Sources.
Europe, Central--History--20th century.
World War, 1914-1918--Peace--Sources.
Princeton subject headings:
Austria--History--20th century--Sources.
Austria--History--20th century.
Charles I, Emperor of Austria, 1887-1922.