APA (7th ed.) Citation

Duffield, W. A., Sass, J. H., & Sorey, M. L. (1994). Tapping the earth's natural heat. U.S. G.P.O..

Chicago Style (17th ed.) Citation

Duffield, Wendell A., J. H. Sass, and M. L. Sorey. Tapping the Earth's Natural Heat. Washington, D.C.: U.S. G.P.O., 1994.

MLA (9th ed.) Citation

Duffield, Wendell A., et al. Tapping the Earth's Natural Heat. U.S. G.P.O., 1994.