TY  - RPRT
TI  - Tapping the Earth's natural heat
AU  - Wendell A. Duffield
AU  - J.H. Sass
AU  - M.L. Sorey
PY  - 1994
DO  - 10.3133/cir1125
UR  - https://pubs.usgs.gov/publication/cir1125
ID  - cir1125
ER  -