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2. Nonfatal traumatic brain injuries from sports and recreation activities—United States, 2001–2005;CDC;MMWR Morb Mortal Wkly Rep,2007
3. 1981-82-2007-08 NCAA sports sponsorship and participation rates report;DeHaas,2009
4. Participation in high school sports increases again; confirms NFHS commitment to stronger leadership;NFHSA,2008
5. Sex differences and the incidence of concussions among collegiate athletes;Covassin;J Athl Train,2003