@misc{indiciaed3a694349898,
  title = {Bouguer gravity map of parts of Maricopa, Pima, Pinal, and Yuma Counties, Arizona},
  author = {D. L. Peterson},
  year = {1968},
  doi = {10.3133/gp615},
  url = {https://pubs.usgs.gov/publication/gp615},
  note = {Source identifier: gp615}
}