The following bibliography does not attempt to be comprehensive but highlights useful works for further study. Substantial bibliographies are found in McCulloch (1962), Clark and McMunn (1989), Hassig (1995). Baxter (1998) and Clark (2006).
The Medieval Bestiary website, hosted by David Badke, contains a very extensive list of sources, many with annotation: http://bestiary.ca/biblios/biblioauthor.htm. This is the easiest bibliographical source to access.