13. For an informative study of the publication history of these six volumes, see Peggy Daub, “The Publication Process and Audience for C. P. E. Bach’s Sonaten für Kenner und Liebhaber,” in Bach Perspectives, II: J. S. Bach, the Breitkopfs, and Eighteenth-Century Music Trade, ed. George Staufer (Lincoln and London: University of Nebraska Press, 1996), 65–83.