http://en.wikipedia.org/wiki/Blood_pressure

http://www.americanheart.org/presenter.jhtml?identifier=4473

http://www.nlm.nih.gov/medlineplus/ency/article/003398.htm

http://www.answers.com/topic/blood-pressure

http://www.nhlbi.nih.gov/health/dci/Diseases/Hbp/HBP_WhatIs.html

http://www.americanheart.org/presenter.jhtml?identifier=2112

http://www.medicinenet.com/low_blood_pressure/article.htm

http://www.lifeclinic.com/focus/blood/whatisit.asp

http://www.medicinenet.com/high_blood_pressure/article.htm

http://familydoctor.org/handouts/128.html