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 Youngstown Vindicator reported on Sunday that the lack of a drug-free work force is creating problems as drilling companies begin hiring.
Nine of 10 unskilled workers in Columbiana County cannot pass the urine test, the paper said.
For higher-skilled positions, two of three applicants will likely fail the drug screening, experts told the newspaper.
In some cases, welders and pipe fitters have been brought to Ohio from other areas because the industry cannot find enough skilled or drug-free workers, the paper said.
Marijuana and pain killers are the most common drugs reported.
Such tests cost companies about $40 per test.