According to STAEHELIN 1973, 82, this Mass is Gaffurius's "Imperatrix gloriosa" listed in BERWIN-HIRSCHFELD 1892, 91. The Mass is also cited among Gaffurius's "missae" by EITNER 1900-04, vol. 4, 122 (s.v. "Gafori [Gafurio], Franchino"). For the problems concerning the attribution, see http://www.motetcycles.ch/cycle/422. The two previous motets, this Mass and the subsequent motet as well ([IV.4]-[IV.7]) belong together forming a hybrid cycle (see ibid.).