TY  - RPRT
TI  - Digital assessment of northern and central Appalachian basin coals
AU  - L.F. Ruppert
AU  - S.J. Tewalt
AU  - L. J. Bragg
AU  - R.N. Wallack
PY  - 1999
UR  - https://pubs.usgs.gov/publication/70021220
ID  - 70021220
ER  -