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 number of active Pennsylvania gas drilling rigs is continuing to decline, but the number in West Virginia is increasing.
Baker Hughes Inc., a Texas-based oil-field services company, reported on Monday that there are 95 drilling rigs operating in Pennsylvania, down one from the previous week.
That's also down from 108 a year ago,
There were 22 rigs in West Virginuia, up one from the previous week and up four from a year ago.