Columbia subject headings:
Mahler, Gustav, 1860-1911.
Musicians--Correspondence.
Strauss, Richard, 1864-1949.
Harvard subject headings:
Composers--Austria--Correspondence
Composers--Germany--Correspondence
Mahler, Gustav, 1860-1911--Correspondence.
Mahler, Gustav, 1860-1911.
Strauss, Richard, 1864-1949
Strauss, Richard, 1864-1949--Correspondence.
Princeton subject headings:
Mahler, Gustav, 1860-1911.
Musicians--Correspondence.
Strauss, Richard, 1864-1949.