TY  - RPRT
TI  - Historical trends of U.S. mineral statistics for gold, silver, and the rare earth elements
AU  - D.Z. Piper
AU  - E.B. Amey
AU  - H.E. Hilliard
AU  - J.B. Hedrick
AU  - N. Galtseva
AU  - W. J. Nokleberg
PY  - 1999
DO  - 10.3133/ofr9939
UR  - https://pubs.usgs.gov/publication/ofr9939
ID  - ofr9939
ER  -