* [http://www.earthworksaction.org/pubs/OGAPMarcellusShaleReport-6-12-08.pdf Shale Gas: Focus on the Marcellus Shale/ "Lisa Sumi and the Oil and Gas Accountability Project of Earthworks"].
* [http://www.un-naturalgas.org/ "Un-Natural Gas"], which notes among other things that there "is nothing natural about what the methane extraction process invented by Halliburton does to water, air, & living things."
* [http://www.propublica.org/article/natural-gas-drilling-debate-heats-up-read-our-guide/ "Best of ProPublica's Natural Gas Reporting"]
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