Bibliography

http://notexactlyrocketsciencexd.blogspot.com/2013/04/why-red-blood-cells-look-like-donuts.html

http://faculty.stcc.edu/AandP/AP/AP2pages/Units18to20/blood/redblood.htm

http://www.newenglandblood.org/helping/redcells.htm

http://kidshealth.org/kid/htbw/heart.html#

http://www.kidzworld.com/article/1240-how-blood-carries-oxygen

Heart Decide app

https://media.goboard.io/simple%20lung%20diagram