@misc{indiciae8120193bb8b0,
  title = {Rock units of the Precambrian basement in Colorado},
  author = {Ogden Tweto},
  year = {1987},
  doi = {10.3133/pp1321a},
  url = {https://pubs.usgs.gov/publication/pp1321A},
  note = {Source identifier: pp1321A}
}