In the original Cantus index for this manuscript, differentiae were assigned codes in accordance with the Sarum Tonale.
Edwards, Owain Tudor. Inventory of Aberystwyth, Llyfrgell Genedlaethol Cymru (National Library of Wales), 20541 E. Revised and expanded by Keith Glaeske, Charles Downey, and Lila Collamore. In: Cantus: A 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-).
Frere, Walter Howard, ed. The Use of Sarum, II. The Ordinal and Tonale. Cambridge: Cambridge University Press, 1901.
National Library of Wales MS. 20541 E: The Penpont Antiphonal. With an Introduction by Owain Tudor Edwards. Publications of Mediaeval Musical Manuscripts, No. 22 (Facsimile Reproduction of the Manuscript). Ottawa: The Institute of Mediaeval Music, 1997.
Standardized manuscript tonary completed by Rebecca Shaw (Dalhousie University) on February 22, 2018. Edited by Jennifer Bain, Sister Ilaria Culshaw, Lucia Denk, Andrea Klassen, and Brayden Olson (Dalhousie University) on August 29, 2019.