@misc{indiciae11a1b172a519,
  title = {Preliminary geologic map of the Twin Buttes quadrangle, Pima County, Arizona},
  author = {John R. Cooper},
  year = {1970},
  doi = {10.3133/ofr7090},
  url = {https://pubs.usgs.gov/publication/ofr7090},
  note = {Source identifier: ofr7090}
}