@misc{indiciae373378f9cbc6,
  title = {Coal reserves of Colorado tabulated by bed},
  author = {Edwin R. Landis and George C. Cone},
  year = {1971},
  doi = {10.3133/ofr71178},
  url = {https://pubs.usgs.gov/publication/ofr71178},
  note = {Source identifier: ofr71178}
}