Sources: TrentC 89, fols. 330v-339r (1460-63); PragP 47, fols. 152v-161r; ModE M.1.13, fols. 104v-117r.
Edition: Denkmäler der Tonkunst in Österreich, 134 vols. to date (Vienna: Österreichischer-Bundesverlag, 1894- ), 22: 28-69.
ModE M.1.13, although copied much later than either TrentC 89 or PragP 47, preserves what is evidently the older and more complete version of the Mass. The Trent/Prague version has adapted one of the two equal Contra parts into a more modern Contratenor bassus, bringing down its overall range by approximately a fifth, at the expense of several imitations in the upper range of the original voice.
Dating taken from Wegman. Agnus dei reflects differences in ModE M.1.13.
Based on anonymous 4-voice motet "O pater eterne" (http://elvis.music.mcgill.ca/node/540).