http://www.bbc.co.uk/sn/tvradio/programmes/spaceodyssey/healtheffects.shtml
http://library.thinkquest.org/03oct/02144/text/travel/body.htm
http://waltonaero.wikidot.com/522group-4
http://www.nsbri.org/HumanPhysSpace/introduction/intro-bodychanges.html