@misc{indiciaecd552481008f,
  title = {A borehole geophone leveling device},
  author = {Hsi-Ping Liu and R.E. Westerlund and Joe B. Fletcher and R.E. Warrick},
  year = {1986},
  doi = {10.3133/ofr86351},
  url = {https://pubs.usgs.gov/publication/ofr86351},
  note = {Source identifier: ofr86351}
}