TY  - RPRT
TI  - Digital data sets describing principal aquifers, surficial geology, and ground-water regions of the conterminous United States
AU  - Rick M. Clawges
AU  - Curtis V. Price
PY  - 1999
DO  - 10.3133/ofr9977
UR  - https://pubs.usgs.gov/publication/ofr9977
ID  - ofr9977
ER  -