@misc{indiciae1c33099a7a51,
  title = {Maps of the Boulder County tungsten district, Colorado},
  author = {T. S. Lovering},
  year = {1942},
  doi = {10.3133/ofr4223},
  url = {https://pubs.usgs.gov/publication/ofr4223},
  note = {Source identifier: ofr4223}
}