- Felix Salzer papers /
- Series 2: Heinrich Schenker Nachlass /
- Sub-series 4: Analyses of Beethoven, Brahms, Haydn, and Mozart (Mappe 27) /
- Beethoven /
- 27/16 /
- Recto: Notes, Piano Sonata in Ab major, op. 26; "1. Satz, Thema (Willfort) in Heft II Url. Tafeln"