@misc{indiciae7cb38c3ff3f5,
  title = {Preliminary geologic map of the Peru quadrangle, Berkshire and Hampshire counties, Massachusetts},
  author = {Stephen A. Norton},
  year = {1974},
  doi = {10.3133/ofr7493},
  url = {https://pubs.usgs.gov/publication/ofr7493},
  note = {Source identifier: ofr7493}
}