1. National Center for Health Statistics. Health United States 2003 . Hyattsville Md: National Center for Health Statistics; 2003. Available at: http://www.cdc.gov/nchs/hus.htm. Accessed May 22 2004.
2. US Department of Health and Human Services. Healthy People 2010: Understanding and Improving Health. 2nd ed. Washington DC: US Government Printing Office; 2000.
3. US Preventive Services Task Force. Guide to Clinical Preventive Services. 3rd ed. Periodic Update. Washington DC: Agency for Healthcare Research and Quality; 2004.