@misc{indiciaeacf694828ecc,
  title = {Isostatic residual gravity map of the Santa Ana 1:100,000 scale quadrangle, California},
  author = {Victoria E. Langenheim and R. H. Chapman and R. F. Sikora and D. A. Ponce and E.T. Dixon},
  year = {1991},
  doi = {10.3133/ofr91555},
  url = {https://pubs.usgs.gov/publication/ofr91555},
  note = {Source identifier: ofr91555}
}