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.
A proposed 250-mile pipeline from Northeast Ohio to Michigan and Ontario is already under fire from environmental groups.
The natural gas pipeline was proposed earlier this week by Enbridge Inc. DTE Energy and Spectra Energy.
The estimated cost: $1.2 billion to $1.5 billion.
The pipeline has been attacked by Cleveland-based EcoWatch and by Food & Water Watch, a national eco-group.
It would cause health and environmental problems in Ohio and allow companies to export natural gas to Canada, the eco-groups said.
The companies involved have defended the project.