@misc{indiciaefa6e542c2631,
  title = {USGS tiltmeter networks: operation and maintenance},
  author = {Carl E. Mortensen and E.Y. Iwatsubo and M.J.S. Johnston and G.D. Myren and V.G. Keller and T.L. Murray},
  year = {1977},
  doi = {10.3133/ofr77655},
  url = {https://pubs.usgs.gov/publication/ofr77655},
  note = {Source identifier: ofr77655}
}