@misc{indiciaeee0f9a70fa6b,
  title = {Transcontinental geophysical survey (35°-39° N): Bouguer gravity map from 74° to 87° W longitude},
  author = {the U.S. Air Force Aeronautical Chart and Information Center},
  year = {1968},
  doi = {10.3133/i535b},
  url = {https://pubs.usgs.gov/publication/i535B},
  note = {Source identifier: i535B}
}