@misc{indiciaecbbf6767cbe9,
  title = {Map showing wells drilled for oil and gas deeper than 15,000 feet in the conterminous United States and offshore},
  author = {K.I. Cunningham},
  year = {1987},
  doi = {10.3133/om219},
  url = {https://pubs.usgs.gov/publication/om219},
  note = {Source identifier: om219}
}