APA
Wendell A. Duffield ; John H. Sass ; Michael L. Sorey, . (1994). Tapping the Earth´s Natural Heat. Denver: U.S. Geological Survey.
Chicago
Wendell A. Duffield ; John H. Sass ; Michael L. Sorey, . 1994. Tapping the Earth´s Natural Heat. Denver: U.S. Geological Survey.
Harvard
Wendell A. Duffield ; John H. Sass ; Michael L. Sorey, . (1994). Tapping the Earth´s Natural Heat. Denver: U.S. Geological Survey.
MLA
Wendell A. Duffield ; John H. Sass ; Michael L. Sorey, . Tapping the Earth´s Natural Heat. Denver: U.S. Geological Survey. 1994.
