RT Journal Article SR Electronic T1 Cycling without a helmet JF Canadian Medical Association Journal JO CMAJ FD Canadian Medical Association SP 1407 OP 1407-b DO 10.1503/cmaj.1060053 VO 175 IS 11 A1 Sarah Giles YR 2006 UL http://www.cmaj.ca/content/175/11/1407.3.abstract