http://gdr.nrcan.gc.ca/gamma/about_e.php
http://www.radiationanswers.org/radiation-introduction/types-of-radiation/types-of-emissions.html
http://www.darvill.clara.net/nucrad/types.htm
http://uraniumsa.org/about/radioactivity.htm
http://www.wisegeek.com/what-is-radioactivity.htm
http://chemistry.about.com/od/chemistryfaqs/f/radioactivity.htm
http://www.state.nj.us/llrwsb/radwrld.htm
http://www.buzzle.com/articles/list-of-radioactive-elements.html
