Wegmancommentary: Tijdschrift van de Vereniging voor Nederlandse Muziekgeschiedenis, 33 (1983): 29-48, at 44-47.
The earliest known source for Josquins Mass, BasU F.IX.55, was copied c.1507-10. The setting is anonymous there, but it was attributed to Josquin by Heinrich Faber, in 1548. Judging from the style of the Credo, the only complete movement to survive, it is hard to imagine who else would have written this setting in the early 1500s: this is as vintage Josquin as anything Ive heard. But the editors of the New Josquin Edition have preferred to blunder on the side of caution, and have rejected the work as definitely not by Josquin.
Based on anonymous monophonic Lied "Rosina" (http://elvis.music.mcgill.ca/node/1294)