Columbia subject headings:
Harvard subject headings:
Ammann, Walter Richard, 1888-1953--Correspondence.
Arx, Cäsar von, 1895-1949--Correspondence.
Authors, Swiss--20th century--Correspondence
Princeton subject headings:
Ammann, Walter Richard, 1888-1953--Correspondence.
Arx, Cäsar von, 1895-1949--Correspondence.
Dramatists, Swiss--20th century--Correspondence.