@misc{indiciae74cad0cf9466,
  title = {Preliminary geologic map of the Berthoud Pass quadrangle, Clear Creek and Grand Counties, Colorado},
  author = {P. K. Theobald},
  year = {1965},
  doi = {10.3133/i443},
  url = {https://pubs.usgs.gov/publication/i443},
  note = {Source identifier: i443}
}