@misc{indiciae2ff1e4ba2aba,
  title = {Geology of the eastern part of the Harold D. Roberts Tunnel, Colorado (Stations 690+00 to 1238+58)},
  author = {Lawrence Allen Warner and Charles Sherwood Robinson},
  year = {1981},
  doi = {10.3133/pp831d},
  url = {https://pubs.usgs.gov/publication/pp831D},
  note = {Source identifier: pp831D}
}