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.
California's biggest environmental groups gathered in Sacramento and called for a moratorium on hydraulic fracturing or fracking until the impacts are better understood.
Today's gathering is the last in a series of workshops on fracking by the California Department of Conservation's Division of Oil, Gas and Geothermal Resources.
It is considering new rules on the practice that is mostly unregulated in Calidfornia.
It is estimated that 600 wells were fracked last year, mostly around Bakersfield.