Columbia subject headings:
Haenisch, Konrad, 1876-1925--Correspondence.
Socialists--Germany--Correspondence.
Harvard subject headings:
Haenisch, Konrad, 1876-1925--Correspondence.
Socialists--Germany--Correspondence.
Princeton subject headings:
Haenisch, Konrad, 1876-1925.
Socialists--Germany--19th century--Biography.
Socialists--Germany--20th century--Biography.
Socialists--Germany--Correspondence.