@misc{indiciaeb957fcb487cf,
  title = {Geological and Geographical Atlas of Colorado and portions of adjacent territory},
  author = {Ferdinand Vandeveer Hayden and Julius Bien},
  year = {1881},
  doi = {10.3133/70039833},
  url = {https://pubs.usgs.gov/publication/70039833},
  note = {Source identifier: 70039833}
}