References
Pidwirny, Michael http://www.arts.ouc.bc.ca/geog/G121/3k.html
CST Web Team http://cst.lanl.gov/CST/imagemap/periodic/7.html
Lide, David R. http://www.crl.com/~peters/periodic/7.htm
Air Products and Chemicals, Inc. http://www.airproducts.com/gases/nitrgen.html
http://chemfinder.camsoft.com/cgi-win/cfserver.exe/
Winter, Mark http://www.chemplace.com/periodic/N.html
Winter, Mark http://www.shef.ac.uk/chemistry/web-elements/index-fr.html