The following references relate to an article in PCPG's 2nd quarter 2010 newsletter, The Marcellus Shale -- On a First-Name Basis:
Engelder, T. 2008. Appalachian Spring A new shale play emerges in the East. Platts Appalachian Gas Conference, Pittsburgh, PA. October 29-30, 2008.
Harper, John A. (2008). The Marcellus Shale - An Old "New" Gas Reservoir in Pennsylvania. Pennsylvania Geology, Volume 38, Number 1. Pennsylvania Bureau of Topographic and Geologic Survey.
Laughrey, Christopher D., Billman, Dan A., and Canich, Michael R. 2004. Petroleum geology and geochemistry of the Council Run gas field, north central Pennsylvania. AAPG Bulletin, v. 88, No. 2 (February 2004), pp. 213-239.
Milici, R.C. 2005. Assessment of Undiscovered Natural Gas Resources in Devonian Black Shales, Appalachian Basin, Eastern U.S.A. U.S. Geological Survey Open File Report 2005-1268, version 1.0. http://pubs.usgs.gov/of/2005/1268/2005-1268.pdf
Milici, R.C., Ryder, R.T., Swezey, C.S., Charpentier, R.R., Cook, T. A., Crovelli, R.A., Klett, T.R., Pollastro, R.M., and Schenk, C.J. 2003. Assessment of undiscovered oil and gas resources of the Appalachian Basin Province, 2003: U.S. Geological Survey Fact Sheet FS-009-03, 2 p.
Portfolio.com. 2010. One Stubborn Texan, One Energy Revolution. http://www.portfolio.com/industry-news/energy/2010/05/25/cracking-stubborn-rocks-to-unlock-natural-gas-could-revolutionize-american-energy-mix.