Gregorian chant in the service of the church
The beginnings of Gregorian chant; other rites and other sorts of chants
Tradition and innovation in medieval chant : from the ninth to the sixteenth century
Thinking about Gregorian chant in the Middle Ages, and notating it
New chants for new times : from the sixteenth century to the present; aspects of performance.
Gregorian chant by David Hiley. ISBN 9780521690355. Published by Cambridge University Press in 2009. Publication and catalogue information, links to buy online and reader comments.