TY  - RPRT
TI  - A simplified economic filter for open-pit mining and heap-leach recovery of copper in the United States
AU  - Keith R. Long
AU  - Donald A. Singer
PY  - 2001
DO  - 10.3133/ofr01218
UR  - https://pubs.usgs.gov/publication/ofr01218
ID  - ofr01218
ER  -