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.
Anadarko Petroleum has offered $15 million to the state of Pennsylvania for surface access to part of Loyalsock State Forest.
The company owns half of the mineral rights in an area of the forest known as the Old Logger's Path.
Environmentalists and the state are on opposite sides in the debate over whether the state can allow drilling in that area.
Click here to read more from the Allegheny Front.