Jeff Kuyken and list: Just ran across an on-line copy of Stoffler OC shock classification here: http://www.museum.hu-berlin.de/home.asp?page=http://www.museum.hu-berlin.de/ min/forsch/forschprojects/planet/asteroidmeteor.asp?lang=1 But it's a 2001 update, not the original '91. Good read, though.