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.
A new study from the Energy Institute at the University of Texas at Austin has found "no evidence" of hydraulic fracturing or fracking leading to groundwater contamination.
Lead author Charles Groat said: "We found no direct evidence of the hydraulic fracturing itself -- the practice of fracturing the rocks -- had contaminated the shallow aquifer."
He added in a statement: "What we've tried to do is separate fact from fiction."
The results were circulated by Energy in Depth, a national pro-drilling industry group.
Tow Stewart, executive vice president of the Ohio Oil and Gas Association and executive director of Energy in Depth-Ohio, said the report validates what regulators and other scientists have long maintained.
"The University of Texas study confirms what previous studies have stated in its conclusion that hydraulic fracturing has not directly been tied to one instance of groundwater contaminat," he said in a statement.
The report says that many problems ascribed to hydraulic fracturing are related to processes common to oil-and-gas drilling operations, such as casing failures and poor cement jobs.
Click here for more information on the Texas study.