Columbia subject headings:
Authors, German--20th century--Correspondence.
Becher, Johannes Robert, 1891-1958--Correspondence.
Harvard subject headings:
Authors, German--20th century--Correspondence
Becher, Johannes Robert, 1891-1958--Correspondence.
Princeton subject headings:
Authors, German--20th century--Correspondence.
Becher, Johannes Robert, 1891-1958--Correspondence.