Graduale triplex (1979). Tournai: Desclée& Socii. ISBN 2-85274-094-X, a special edition of the Graduale Romanum with chant notation in three forms, one above the other, for easy comparison: Laon, St. Gall, and square note
Liber usualis (1953). Tournai: Desclée& Socii.
Paléographie musicale, ISBN 2-85274-219-5, facsimiles of early adiastamatic chant manuscripts
Apel, Willi. Gregorian Chant. Bloomington, IN: Indiana University Press. 1990. ISBN 0-253-20601-4.
Constantin Floros, "Universale Neumenkunde" (Universal Theory of Neumes); three-volume covering all major styles and schools of neumatic musical notation in three major divisions: Byzantine, Gregorian and Slavic.* Hiley, David (1990). Chant. In Performance Practice: Music before 1600, Howard Mayer Brown and Stanley Sadie, eds., pp. 37-54. New York: W.W. Norton & Co. ISBN 0-393-02807-0
Hiley, David. Western Plainchant: A Handbook. Clarendon Press. 1995. ISBN 0-19-816572-2.
Mahrt, William P. (2000). Chant. In A Performer's Guide to Medieval Music, Ross Duffin, ed., pp. 1-22. Bloomington, IN: Indiana University Press. ISBN 0-253-33752-6
McKinnon, James, ed. Antiquity and the Middle Ages. Prentice Hall. 1990. ISBN 0-13-036153-4.
Wagner, Peter. (1911) Einführung in die Gregorianischen Melodien. Ein Handbuch der Choralwissenschaft. Leipzig: Breitkopf & Härtel.
Wilson, David. Music of the Middle Ages. Schirmer Books. 1990. ISBN 0-02-872951-X.
