Census Bureau (US). U.S. Census 2009: School enrollment in the United States 2009 [cited 2012 Mar 16]. Available from: URL: http://www.census.gov/hhes/school
3.
Department of Health and Human Services (US). Preventing tobacco use among youth and young adults: A report of the Surgeon General. Atlanta: HHS, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health (US); 2012. Also available from: URL: http://www.surgeongeneral.gov/library/preventing-youth-tobacco-use/full-report.pdf [cited 2012 Mar 15].
Substance Abuse and Mental Health Service Administration (US). 2010 National Survey on Drug Use and Health. Rockville (MD): Department of Health and Human Services (US), SAMHSA; 2011.