@misc{indiciaeed92206b536d,
  title = {Geologic map of the Powder River basin and surrounding area, Wyoming, Montana, South Dakota, North Dakota, and Nebraska},
  author = {M.S. Ellis and R. B. Colton},
  year = {1994},
  doi = {10.3133/i2298},
  url = {https://pubs.usgs.gov/publication/i2298},
  note = {Source identifier: i2298}
}