RT Journal Article SR Electronic T1 Concussion in youth ice hockey: It’s time to break the cycle JF Canadian Medical Association Journal JO CMAJ FD Canadian Medical Association SP 921 OP 924 DO 10.1503/cmaj.110282 VO 183 IS 8 A1 Johnson, L. Syd M. YR 2011 UL http://www.cmaj.ca/content/183/8/921.abstract