Some recent research into the anti-mendicant controversies reminded me just how much Thomas knew about and employed canon law, all throughout his career. I have been reading Anders Winroth's important book, The Making of Gratian's Decretum (Cambridge: Cambridge University Press, 2000), and just found out that the author has a home page for Gratian studies. One of the many gems in the site is a lecture that Winroth gave at the Twelfth International Congress of Medieval Canon Law in 2004, entitled "Recent work on the making of Gratian's Decretum." To read the lecture (in PDF format) is to get a refresher course in Gratian and his work. I believe that I have mentioned before that the entire Decretum is on-line: a crucial resource.