Is it Bach or isn’t it? And if so, which Bach? After the sonata was temporarily moved to the appendix of the BWV, it is now “rehabilitated” in the new BWV³.
Barthold Kuijken sets out all the arguments on this crucial question with impressive expertise in his afterword. “In summary”, writes the author, “BWV 1031 is untypical of C. P. E. Bach (and W. F. Bach), too thin for J. S. Bach and too good for Quantz. [...] In the end, we can comfort ourselves with the thought that in spite of all these considerations, the piece remains the same […].”

“I am very, very impressed by the Breitkopf / Kuijken edition of Bach's flute sonatas that I bought yet another copy when I discovered to my horror that I was en route to a recital abroad without my music. Breitkopf (make sure it's the new edition by Barthold Kuijken you buy) publish each sonata separately, which inevitably works out more expensive, but with the amount of extra information and inclusion of flute and bass parts together this is a bargain. Everyone should have these, even if they already possess other editions.” (Pan Magazine)