1. 1) Environmental Literacy Council, http://www.enviroliteracy.org/index.php
2. 2) Wikipedia, The Free Encyclopedia, www.wikipedia.org
3. 3) American Coal Ash Association, http://www.acaa-usa.org/
4. 4) European Coal Combustion Products Association, http://www.ecoba.com/index.html
5. 5) Ash Development Association of Australia, http://www.adaa.asn.au/welcome.htm