Columbia subject headings:
Authors, Swiss--20th century--Correspondence.
Burckhardt, Carl Jacob, 1891-1974--Correspondence.
Harvard subject headings:
Authors, Swiss--20th century--Correspondence
Burckhardt, Carl Jacob, 1891-1974--Correspondence.
Historians--Switzerland--Correspondence.
Princeton subject headings:
Authors, Swiss--20th century--Correspondence.
Burckhardt, Carl Jacob, 1891-1974. Correspondence.