Columbia subject headings:
Authors, German--20th century--Correspondence.
Keller, Philipp, 1891-1973--Correspondence.
Harvard subject headings:
Authors, German--20th century--Correspondence
Keller, Philipp, 1891-1973--Correspondence.
Princeton subject headings:
Authors, German--20th century--Correspondence.
Fiction.
Keller, Philipp, 1891-1973--Correspondence.