@misc{indiciae92cee2f59136,
  title = {Geologic map of the Black Ridge quadrangle, Delta and Montrose Counties, Colorado},
  author = {Wallace R. Hansen},
  year = {1968},
  doi = {10.3133/gq747},
  url = {https://pubs.usgs.gov/publication/gq747},
  note = {Source identifier: gq747}
}