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.
Carroll County is the first Ohio county to hit 100 permits for horizontal wells in the Utica shale.
The Ohio Department of Natural Resources' Division of Oil and Gas Resources Managament has approved 100 permits for Carroll County.
Staterwide, the state has approved 297 permits, of which 105 wells have been drilled through July 23.
Those 297 permits have been issued since December 2009.
The other top Ohio counties for permits are Columbiana, 47; Jefferson, 26; Harrison, 24; Monroe, 16; Guernsey, 13; Stark, Noble and Mahoning, all with 12; and Portage, 8.
Ohio has also approved 17 additional Marcellus shale permits, of which seven wells have been drilled.