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WikiPedia: Nitơ http://pubs.nrc-cnrc.gc.ca/rp/rppdf/v03-178.pdf http://box27.bluehost.com/~edsanvil/wiki/index.php... http://www.bookrags.com/sciences/sciencehistory/ai... http://www.cartalk.com/content/columns/Archive/199... http://www.findarticles.com/p/articles/mi_m1200/is... http://books.google.com/?id=6eF4AfEwF4YC&pg=PA338 http://books.google.com/?id=TuMa5lAa3RAC&pg=PA508 http://books.google.com/?id=qmZDpnV-sYYC&pg=PA283 http://books.google.com/?id=yS_m3PrVbpgC&pg=PR15 http://auto.howstuffworks.com/question594.htm