@misc{indiciae3cecc84c9153,
  title = {Complete Bouguer gravity anomaly map of the area north of the Grand Canyon in Arizona},
  author = {Peter Popenoe},
  year = {1968},
  doi = {10.3133/ofr68216},
  url = {https://pubs.usgs.gov/publication/ofr68216},
  note = {Source identifier: ofr68216}
}