APA (7th ed.) Citation

Duffield, W. A., & Sass, J. H. (2003). Geothermal energy: Clean power from the Earth's heat. U.S. Geological Survey.

Chicago Style (17th ed.) Citation

Duffield, Wendell A., and J. H. Sass. Geothermal Energy: Clean Power from the Earth's Heat. Menlo Park, Calif.: U.S. Geological Survey, 2003.

MLA (9th ed.) Citation

Duffield, Wendell A., and J. H. Sass. Geothermal Energy: Clean Power from the Earth's Heat. U.S. Geological Survey, 2003.