Columbia subject headings:
Duisberg, Carl, 1861-1935--Correspondence.
Industrialists--Germany--Correspondence.
Harvard subject headings:
Duisberg, Carl, 1861-1935--Correspondence.
Industrialists--Germany--Correspondence.
Princeton subject headings:
Duisberg, Carl, 1861-1935--Correspondence.
Industrialists--Germany--Correspondence.