10. Nicholas Marston, Beethoven’s Piano Sonata in E, Op. 109 (Oxford: Oxford University Press, 1995), 46; “Schenker and Forte Reconsidered: Beethoven’s Sketches for the Piano Sonata in E, Op. 109,” 19th Century Music 10 (1986): 24–42, esp 31, which speaks of “the remarkable intrusion of the second group … at m. 9.”