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 Institute of Medicine announced on Monday that it will examine the hydraulic fracturing or fracking processto drill for natural gas to determine whether the process "poses potential heatlh challenges."
The news came from a spokesman for the federal Centers for Disease Control and Prevention.
The institute is part of the National Academy of Sciences and advises U.S. government agencies on health issues.
The institute intends to look at water and air contamination issues surrounding drilling for natural gas and oil.
Federal health officials have gotten complaints from people in areas where gas wells have been drilled. That includes complaints of nausea, respiratory issues and irritating odors.