@misc{indiciaeb6581f88bd23,
  title = {Geologic map of the Twin Buttes Quadrangle, southwest of Tucson, Pima County, Arizona},
  author = {J.R. Cooper},
  year = {1973},
  doi = {10.3133/i745},
  url = {https://pubs.usgs.gov/publication/i745},
  note = {Source identifier: i745}
}