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.
About 75 residents protested on Thursday in Butler, Pa., after an energy company said it would no longer provide replacement water to some residents.
The residents of The Woodslands, a rural community in southern Butler County about 30 miles north of Pittsburgh, picketed outside the offices of Rex Energy Inc.
The company, based in State College, Pa., had provided about a dozen families with 800-gallon plastic tanks and filled them regularly for a year.
But the company drained and removed the tanks, citing a series of test results that fail to establish a link between drilling and water problems in Connoquenessing Township.
The state Department of Environmental Protection began tests in early 2011, but couldn't link contamination to the Rex drilling, officials said.
A grass-roots group, Marcellus Outreach Butler, wants the tests redone. That group and Protecting Our Waters, a Philadelphia-based eco-group, want the U.S. Environmental Protection Agency to intervene and to provide drinking water.
Residents say their water problems began after the drilling got under way.