Mode of access: Internet from the National Library of Medicine and Agency for Healthcare Research and Quality web sites. Addresses as of 4/28/04: http://text.nlm.nih.gov/ftrs/dbaccess/tbi2ssum (NLM), http://www.ahrq.gov/clinic/epcsums/tbisum2.htm (AHRQ); current access to AHRQ version available via PURL.