@misc{indiciaeed6356a4a47b,
  title = {Digital data sets describing principal aquifers, surficial geology, and ground-water regions of the conterminous United States},
  author = {Rick M. Clawges and Curtis V. Price},
  year = {1999},
  doi = {10.3133/ofr9977},
  url = {https://pubs.usgs.gov/publication/ofr9977},
  note = {Source identifier: ofr9977}
}