The effect of helmets on the risk of head and neck injuries among skiers and snowboarders: a meta-analysis. Kelly Russell MSc, Josh Christie BHSc, Brent E. Hagel PhD CMAJ 2010. DOI:10.1503/cmaj.091080. Early release, published at www.cmaj.ca on February 1, 2010. Subject to revision. http://www.cmaj.ca/cgi/rapidpdf/cmaj.091080v1?ijkey=8c9f0e4ad93fa38f51cf28f1543b22fd797196b4 [dostęp=2010-05-03]