This is a lovely sonata, I think, one of Schubert's best. But where is the second part - Allegretto? A. Schiff, S. Richter and Z. Kocsis play it as two-part sonata! And I cannot find Allegretto apart.
Answer: The editor of the "Alte Gesamtausgabe" knew only this movement. The second movement "Allegretto", E-major 2/4 was first published in 1907 by Breitkopf & Härtel, Leipzig, the third "Scherzo: Allegro vivace", 3/4, A-flat-major with Trio, D-flat-major in: "Die Musik" XXI, Heft 1, 1928. Thus the Sonata is incomplete. In "British and Continental Music Agencies", Nr. 60, 1948 these three movements were completed by the Rondo in E-major, D 506, but this is not authentic, because the manuscript (now lost) ended with the trio of movement 3. --Molinarius 19:06, 14 September 2011 (UTC)