Folios 44 and 45 were once part of a quire with the bifolio catalogued as https://cantus.uwaterloo.ca/source/698765, with one or two missing bifolios containing the remaining chants for Christmastide. Folios 42 and 43 were part of a later quire in the same source, and have been labelled in the wrong order; originally 43 would have been followed by the inner folios of the quire (containing chants for the first and second weeks of Lent), followed by folio 42. Text is quite effaced on folios 43v, 44v, and 45r.
Laura Albiero, 2020, for Fragmentarium