TY  - RPRT
TI  - Digitizing procedure for the National Coal Resources Data System of the U.S. Geological Survey
AU  - Judy F. Hunter
AU  - Sharon S. Crowley
AU  - Antoinette L. Medlin
PY  - 1981
DO  - 10.3133/ofr811225
UR  - https://pubs.usgs.gov/publication/ofr811225
ID  - ofr811225
ER  -