RT Journal Article SR Electronic T1 Helmet laws and cycle use JF Injury Prevention JO Inj Prev FD BMJ Publishing Group Ltd SP 380 OP 381 DO 10.1136/ip.9.4.380 VO 9 IS 4 A1 D L Robinson YR 2003 UL http://injuryprevention.bmj.com/content/9/4/380.abstract AB