@misc{indiciae4c43a25b3a04,
  title = {Map showing distribution pattern of copper from samples of -80 mesh stream sediment, northern Sonora, Mexico},
  author = {James G. Frisken and R. L. Turner and T. M. Billings and Guillermo Monroy and Benjamin Ponce},
  year = {1977},
  doi = {10.3133/ofr77338},
  url = {https://pubs.usgs.gov/publication/ofr77338},
  note = {Source identifier: ofr77338}
}