RT Journal Article SR Electronic T1 The risk compensation theory and bicycle helmets JF Injury Prevention JO Inj Prev FD BMJ Publishing Group Ltd SP 89 OP 91 DO 10.1136/ip.7.2.89 VO 7 IS 2 A1 Adams, J A1 Hillman, M YR 2001 UL http://injuryprevention.bmj.com/content/7/2/89.abstract AB