Hoffman, M. (n.d.). Picture of the Gallbladder. Retrieved April 24, 2017, from http://www.webmd.com/digestive-disorders/picture-of-the-gallbladder#1.
Laskey, J. (2015, February 16). The Health Benefits of Water. Retrieved April 24, 2017, from http://www.everydayhealth.com/water-health/water-body-health.aspx.
On Your Toes. (n.d.). Retrieved April 24, 2017, from http://www.amnh.org/exhibitions/horse/the-evolution-of-horses/on-your-toes/.
Taylor, K. H. (2011, August 30). Why some people don't get the flu. Retrieved April 24, 2017,from "http://www.nbcnews.com/id/44275043/ns/health-cold_and_flu/t/why-some-people-dont-get-flu/#.WP6fh9LyvIU ".
Whiteman, H. (2013, September 30). Immune response determined by our genes, study shows. Retrieved April 25, 2017, from http://www.medicalnewstoday.com/articles/266746.php.