TY  - RPRT
TI  - Coal mining in the 21st century: Yampa coal field, northwest Colorado
AU  - Michael E. Brownfield
AU  - Edward A. Johnson
AU  - Ronald H. Affolter
AU  - Charles E. Barker
PY  - 1999
UR  - https://pubs.usgs.gov/publication/70068759
ID  - 70068759
ER  -