TY  - RPRT
TI  - Geologic map of the North Keystone mine, Copperopolis, California
AU  - G.R. Heyl
AU  - J. B. Hadley
AU  - G.L. Quick
PY  - 1943
DO  - 10.3133/ofr4341
UR  - https://pubs.usgs.gov/publication/ofr4341
ID  - ofr4341
ER  -