RT Journal Article SR Electronic T1 Concussion in youth hockey JF Canadian Medical Association Journal JO CMAJ FD Canadian Medical Association SP 1175 OP 1175 DO 10.1503/cmaj.111-2053 VO 183 IS 10 A1 L. Syd M. Johnson YR 2011 UL http://www.cmaj.ca/content/183/10/1175.2.abstract