Circulatory picture http://www.urgomedical.com/Pathophysiologies/Compression/The-venous-system/In-the-cardiovascular-system

Blood pressure picture http://www.phschool.com/science/biology_place/biocoach/cardio2/factors.html

Surface area of blood pressure picture http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookcircsys.html

Battery Picture   http://simonlittlegreen.com/blog/tag/toxic-chemicals/

How a battery works picture  http://www.makeitsolar.com/solar-energy-information/07-solar-cells.htm

 John, Hewes. Voltage and Current. 2011 <http://www.kpsec.freeuk.com/voltage.htm>.

Scott, Freeman. Biological Science. San Francisco: Pearson. 2008.

Connie, Allen. Valerie, Harper. Labratory Manual for Anatomy and Physiology, 12th Ed.New Jersey: River Street, Hoboken, 2009.

Giancoli, C. Douglas. Physics: Principles with Applications, 6th Ed. New Jersey: Upper Saddle River, 2005.

Gerard, J. Tortora. Bryan Derrickson. Principles of Anatomy and Physiology, 12th Ed.New Jersey: River Street, Hoboken, 2009.