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 Wall Street Journal reported today that the influx of big drillers is resulting in fewer drilling violations.
Large drillers in Pennsylvania were responsible for 38 regulatory violations per 100 wells drilled, according to state records.
Small drilling companies were reponsible for 132 regulatory violations per 100 wells drilled.
For medium-sized companies, there were 69 violations, according to state records.
The newspaper said the larger companies are more apt to stress safety and compliance.
The state data covers from 2008-2012.