Sources

http://www.propublica.org/special/map-number-of-producing-gas-wells-708

http://www.exxonmobil.com/Corporate/about.aspx

http://blogs.the-american-interest.com/wrm/2011/10/24/fracking-the-good-the-bad-and-the-ugly/

http://www.aei.org/article/economics/benefits-of-hydraulic-fracking/

http://www.nrdc.org/energy/gasdrilling/

http://www.nwf.org/What-We-Do/Energy-and-Climate/Drilling-and-Mining/Natural-Gas-Fracking.aspx

http://www.businessweek.com/articles/2013-04-01/more-evidence-that-fracking-causes-earthquakes

http://geology.gsapubs.org/content/early/2013/03/26/G34045.1.abstract
http://www.savecoloradofromfracking.org/basics/history.html