Information on differentia
The original Cantus index categorizes the differentia in this manuscript by their last note and an arbitrarily assigned number within each mode. Slight variations, including abbreviations, are indicated by a lowercase suffix (e.g., D2, D2a). Differentiae appear in their complete six-syllable form and abbreviated to the last two syllables, "Amen." Abbreviated differentiae are indexed as though they were complete in the Differentiae Database.
de Loos, Ike, Elizabeth Sander, and Andrew Mitchell. Inventory of Aachen (Aix-la-Chapelle), Domarchiv, G 20. Edited by Debra Lacoste and Kate Helsen. In: Cantus Manuscript Database for Latin Ecclesiastical Chant: Inventories of Chant Sources. Directed by Debra Lacoste (2011-), Terence Bailey (1997-2010), and Ruth Steiner (1987-1996). Web developer, Jan Kolácek (2011-).
Microfilm images available by the Landschaftsverband Rheinland (Archivberatungstelle Rheinhland (Film Nr. 12/1999) (March 31, 1991).