Sources
http://www.chemsoc.org/viselements/pages/data/intro_groupviii_data.html
Glenn T. Seaborg and Evans G. Valens, Elements of the Universe, New York, E.P.Dutton & Company: 1965
Atkins, P.W, The Periodic Kingdom, New York, Basic Books: 1995
www.chemicalelements.com/groups/noblegases.htm
www.members.aol.com/webchem/table.htm
www.wvalley.wnyric.org/cinder/kingqueenpic.htm
http://pearl1.lanl.gov/periodic/elements
http://www.nidlink.com/~jfromm/elements/noble.htm