TY  - RPRT
TI  - The U.S. Geological Survey coal quality data base (COALQUAL)
AU  - R. B. Finkelman
AU  - C.L. Oman
AU  - L. J. Bragg
AU  - S.J. Tewalt
PY  - 1994
DO  - 10.3133/ofr94177
UR  - https://pubs.usgs.gov/publication/ofr94177
ID  - ofr94177
ER  -