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.
An Ohio environmental activist has filed a petition with the federal EPA, charging that an Ohio law on oil and gas drilling violates federal law and endangers public health and safety.
Theresa Mills says federal law requires industries to file detailed reports on the hazardous chemicals they use with cities, local emergency management agencies, and local first responders.
But Ohio law says oil and gas drillers need send the information only to the state Department of Natural Resources.
Click here to see more from radio station WKSU-FM.