Caldwell, John. 1992. Plainsong and polyphony 1250-1550. Plainsong in the age of polyphony, edited by Thomas Forrest Kelly, 6-29. Cambridge etc..

Robertson, Anne W. 1992. The Mass of Guillaume de Machaut in the Cathedral of Reims. Plainsong in the Age of Polyphony, Cambridge Studies in Performance Practice. edited by Thomas Forrest Kelly, 100-39. Cambridge: University Press.

Kelly, Thomas Forrest. 1989. The Beneventan Chant.  Cambridge.