Columbia subject headings:
Schumacher, Tony, 1848-1931--Correspondence.
Wagner, Christian, 1835-1918--Correspondence.
Harvard subject headings:
Authors, German--19th century--Correspondence
Authors, German--20th century--Correspondence
Schumacher, Tony, 1848-1931--Correspondence.
Wagner, Christian, 1835-1918--Correspondence.
Princeton subject headings:
Schumacher, Tony, 1848-1931--Correspondence.
Wagner, Christian, 1835-1918--Correspondence.