Columbia subject headings:
Kautsky, Karl, 1854-1938--Correspondence.
Socialism--Europe, Eastern--History--Sources.
Socialists--Germany--Correspondence.
Harvard subject headings:
Kautsky, Karl, 1854-1938--Correspondence.
Socialism--Europe, Eastern--History--Sources.
Socialism--Europe, Eastern--Sources.
Socialists--Germany--Correspondence.
Princeton subject headings:
Kautsky, Karl, 1854-1938--Correspondence.
Socialism--Balkan Peninsula--History--Sources.
Socialism--Hungary--History--Sources.
Socialists--Europe--Correspondence.