@misc{indiciae04ef476beeb7,
  title = {Interpretive aeromagnetic map using the horizontal gradient: Lake City Caldera area, San Juan Mountains, Colorado},
  author = {V.J. Grauch},
  year = {1987},
  doi = {10.3133/gp974},
  url = {https://pubs.usgs.gov/publication/gp974},
  note = {Source identifier: gp974}
}