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.
Reuters reports that Cuadrilla Resources will add earthquake monitors at its drilling sites in the United Kingdom.
That news comes more than a year after the British government ordered the firm to halt hydraulic fracturing or fracking temporarily after nearby minor earthquakes near Blackpool.
The company said it wll use a so-called traffic light signal based on a seismometer network that measures earthquake activity through sound in real time.