RT Journal Article SR Electronic T1 Bias in estimates of seat belt effectiveness JF Injury Prevention JO Inj Prev FD BMJ Publishing Group Ltd SP 263 OP 263 DO 10.1136/ip.8.4.263 VO 8 IS 4 A1 L S Robertson YR 2002 UL http://injuryprevention.bmj.com/content/8/4/263.abstract AB