References
American Petroleum Institute, 8/15/01. “Industry Statistics” . “July Petroleum Facts at A Glance”. Retrieved 27, October. 2000.
Craig, James R., Vaughan, David J., Skinner, Brian J. 2001. Resources of the Earth: Origin, Use, and Environmental Impact. Third Edition. Prentice-Hall, New Jersey. pp 129-189.
DOE Fossil Energy, 9/11/01. “Oil and Gas Research and Development- Probing Deeper, Faster, Smarter”. Retrieved 10, October. 2000.