Columbia subject headings:
Harvard subject headings:
Liebknecht family.
Liebknecht, Karl, 1871-1919
Liebknecht, Sophie, 1884-1964.
Socialists--Germany--Biography
Princeton subject headings:
Communists--Germany--Biography.
Liebknecht, Karl, 1871-1919.
Liebknecht, Sophie, 1884-1964.
Pacifists--Germany--Biography.
Socialists--Germany--Biography.