@misc{indiciaeb974811b7af7,
  title = {Geologic map of the Purgatory Canyon quadrangle, northern Mohave County, Arizona},
  author = {George H. Billingsley},
  year = {1990},
  doi = {10.3133/ofr90540},
  url = {https://pubs.usgs.gov/publication/ofr90540},
  note = {Source identifier: ofr90540}
}