TY  - RPRT
TI  - Ground-water levels in the United States, 1972-74, north-central states
AU  - Members of the Engineering Geology and Ground Water Branches, U.S. Geological Survey
PY  - 1977
DO  - 10.3133/wsp2163
UR  - https://pubs.usgs.gov/publication/wsp2163
ID  - wsp2163
ER  -