Fernand Cabrol: The Mass of the Western Rites: Chapter 9: The Roman Mass from the Eighth to the Sixteenth Century
Fernand Cabrol: The Mass of the Western Rites: Chapter 10: The Rites Derived from the Roman Mass from Ninth-Sixteenth Centuries
Alan Shearer: "The Liturgy as Propaganda at the Turn of the First Millenium A.D."