APA Citation

Duffield, W. A., & Sass, J. H. (2003). Geothermal energy - clean power from the earth's heat. US Geological Survey circular 1249.

Chicago Style Citation

Duffield, Wendell A., and John H. Sass. "Geothermal Energy - Clean Power From the Earth's Heat." US Geological Survey Circular 1249 2003.

MLA Citation

Duffield, Wendell A., and John H. Sass. "Geothermal Energy - Clean Power From the Earth's Heat." US Geological Survey Circular 1249 2003.

Warning: These citations may not always be 100% accurate.