Chesapeake Energy Corp,the Oklahoma-based firm is the No. 1 driller in Ohio.
Rig Count Interactive Map by Baker Hughes, an energy services company.
Shale Sheet Fracking, a Youngstown Vindicator blog.
The Ohio Environmental Council, a statewide eco-group based in Columbus.
Earthjustice, a national eco-group.
People's Oil and Gas Collaborative-Ohio, a grass-roots group in Northeast Ohio.
Concerned Citizens of Medina County, a grass-roots group.
No Frack Ohio, a Columbus-based grass-roots group.
Fracking: Gas Drilling's Environmental Threat by ProPublica, an online journalism site.
Pipeline, blog from Pittsburgh Post-Gazette on Marcellus shale drilling.
Allegheny Front, environmental public radio for Western Pennsylvania.
Kent State University professor Brian Lutz and Duke University professor Martin Doyle have written an op-ed column in the Pittsburgh Post-Gazette on their study of wastewater from the Marcellus shale in Pennsylvania.
The analysis shows that the Marcellus may produce 10 times more wastewater but it is producing 30 times more natural gas.
A conventional gas boom would result in the release of even more contaminants.
Click here to read more from the Pittsburgh Post-Gazette.