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2. 1. American Heart Association. Circulation: a journal of the American Heart Association. Available at: http://www.circulationaha.org. Accessed December 19 2003.
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4. 3. Mayo Clinic web site. Available at: http://www.mayoclinic.com. Accessed December 19 2003.
5. 4. Cleveland Clinic web site. Available at: http://www.clevelandclinic.org. Accessed December 19 2003.