@misc{indiciae7909a412227d,
  title = {Preliminary report on the engineering geology of the Boulder quadrangle, Boulder County, Colorado},
  author = {Maxwell E. Gardner},
  year = {1968},
  doi = {10.3133/ofr68109},
  url = {https://pubs.usgs.gov/publication/ofr68109},
  note = {Source identifier: ofr68109}
}