ummm... I have a few books on the subject kicking around (due to a couple of on- and - off -when- i- have- time writing projects on the Knights templar), ummm the one that I can immediatly see on my "medieval history" bookshelf is Religion in the Medieval West by Bernard Hamilton, which is the first one that I tend to hit if checking on peripheral details.

http://www.amazon.co.uk/Religion-Medieval-West-Bernard-Hamilton/dp/0713164611/ref=sr_1_2?ie=UTF8&qid=1314471555&sr=8-2