@misc{indiciae8272a4a2fa1d,
  title = {Map showing location of sand, gravel, and till pits and quarries in the Hampden quadrangle, Massachusetts-Connecticut},
  author = {Roger B. Colton and Michael J. Mallory},
  year = {1968},
  doi = {10.3133/ofr6957},
  url = {https://pubs.usgs.gov/publication/ofr6957},
  note = {Source identifier: ofr6957}
}