Columbia subject headings:
Harvard subject headings:
Abbe, Ernst, 1840-1905--Correspondence.
Physicists--Germany--Correspondence.
Physics--Germany--History
Weinhold, Adolf Ferdinand, 1841-1917--Correspondence.
Princeton subject headings:
Abbe, Ernst, 1840-1905--Correspondence.
Physicists--Germany--Correspondence.
Physics--Germany--History.
Weinhold, Adolf Ferdinand, 1841-1917--Correspondence.