@misc{indiciaee72187fde7ab,
  title = {Principal facts for gravity profiles near South Penobscot, Maine},
  author = {Robert W. Simpson and Paul LaPierre},
  year = {1979},
  doi = {10.3133/ofr79767},
  url = {https://pubs.usgs.gov/publication/ofr79767},
  note = {Source identifier: ofr79767}
}