@misc{indiciae39187a44f89e,
  title = {Geologic field photograph map of the Grand Canyon region, 1967–2010},
  author = {George H. Billingsley and Gregory Goodwin and Sarah E. Nagorsen and Monica E. Erdman and Jason T. Sherba},
  year = {2019},
  doi = {10.3133/gip189},
  url = {https://pubs.usgs.gov/publication/gip189},
  note = {Source identifier: gip189}
}