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.
The Ohio Department of Natural Resources has approved 13 new permits for Utica shale drilling.
That brings Ohio's permit total to 477 through Dec. 15.
Of that total, 196 wells have been drilled and 45 wells are in production.
A total of 29 rigs are working in Ohio.
Three new permits are in Carroll County, four are in Harrison County and three are in Noble County
The others are Belmont, Monroe and Mahoning, all with one each.
To date, Carroll County has 173 permits; Columbiana County has 66 and Harrison County has 62.
Other Ohio counties are: Jefferson, 31, Guernsey, 24, Monroe, 23, Noble, 17, Mahoning, 16, Portage, 14, Stark, 13, Tuscarawas, 12, and Belmont, 12.