http://www.mtome.com/Publications/PNLA/prolog-digital.pdf http://www.mtome.com/Publications/PNLA/prolog-digital.pdf I just googled that and don't know if it's

http://www.mtome.com/Publications/PNLA/prolog-digital.pdf http://www.mtome.com/Publications/PNLA/prolog-digital.pdf I just googled that and don't know if it's a legitimate source, but I've previously downloaded a copy from the site of one of the authors, so it's probably all right.