TY  - RPRT
TI  - Ground-water levels in the United States, 1967-71, north-central States
AU  - Members of the Engineering Geology and Ground Water Branches, U.S. Geological Survey
PY  - 1973
DO  - 10.3133/wsp2090
UR  - https://pubs.usgs.gov/publication/wsp2090
ID  - wsp2090
ER  -