- Felix Salzer papers /
- Series 2: Heinrich Schenker Nachlass /
- Sub-series 4: Analyses of Beethoven, Brahms, Haydn, and Mozart (Mappe 27) /
- Beethoven /
- 27/20 /
- Booklet: Sketches, Piano Sonata in Ab major, op. 26 ("I. Satz, Variation III u. 4"); in the hand of Angi Elias; markings by Schenker