@misc{indiciae2ce264102b2e,
  title = {Exploratory drilling in the McCallum coal field, Jackson County, Colorado, August-November 1977},
  author = {Dawn H. Madden},
  year = {1977},
  doi = {10.3133/ofr77888},
  url = {https://pubs.usgs.gov/publication/ofr77888},
  note = {Source identifier: ofr77888}
}