@misc{indiciae14318ae87cf8,
  title = {Map showing potential sources of gravel and crushed-rock aggregate in the Boulder-Fort Collins-Greeley area, Front Range urban corridor, Colorado},
  author = {R. B. Colton and H. R. Fitch},
  year = {1974},
  doi = {10.3133/i855d},
  url = {https://pubs.usgs.gov/publication/i855D},
  note = {Source identifier: i855D}
}