1. The energy resources and electric power situation in the United States;Altman;Energy Conversion,1972
2. Minerals Yearbook 1969. Bureau of Mines, U.S. Department of Interior; U.S. Government Printing Office, Washington, D.C.
3. Reference energy systems and resource data for use in the assessment of energy technologies,1972
4. O. Sangesland, private communication.
5. W. F. Heronemus, private communication.