@misc{indiciae964b51435a67,
  title = {Geologic map of the greater Denver area, Front Range urban corridor, Colorado},
  author = {Donald E. Trimble and Michael N. Machette},
  year = {1979},
  doi = {10.3133/i856h},
  url = {https://pubs.usgs.gov/publication/i856H},
  note = {Source identifier: i856H}
}