OJ 11/54, [6] Handwritten letter from van Hoboken to Schenker, dated January 3, 1926

Van Hoboken sends New Year greetings; reports that he is to see in the Paris Conservatory Library the autograph manuscript of Beethoven's "Appassionata" Sonata, which Einstein has apparently already photographed; he will travel to Vienna on January 6 for lesson on January 9.

OJ 11/54, [23] Handwritten letter from Hoboken to Schenker, dated March 21, 1928

Hoboken has still made no progress on photographic work at the Paris Conservatory. — He will go to Rotterdam and Münster. — Speaks of the importance of his Archive work and contacts he has made. Will probably go to a concert featuring music of Alban Berg. — He asks Schenker to intervene with O. E. Deutsch.

Diary entry by Schenker for 12 November 1913