@misc{indiciae63c3ad826b1d,
  title = {Geologic mapping of tunnels using photogrammetry--camera and target positioning},
  author = {Jeffrey A. Coe and Keld S. Dueholm},
  year = {1991},
  doi = {10.3133/ofr9049},
  url = {https://pubs.usgs.gov/publication/ofr9049},
  note = {Source identifier: ofr9049}
}