@misc{indiciae35a1cd2b9a8f,
  title = {Optical Tracker For Longwall Coal Shearer},
  author = {Poulsen, Peter D. and Stein, Richard J. and Pease, Robert E.},
  year = {1989},
  url = {https://ntrs.nasa.gov/citations/19890000251},
  note = {Source identifier: 19890000251}
}