@misc{indiciae790652914749,
  title = {Preliminary bedrock geologic map of the Ipswich Quadrangle, Massachusetts},
  author = {William H. Dennen},
  year = {1975},
  doi = {10.3133/ofr75544},
  url = {https://pubs.usgs.gov/publication/ofr75544},
  note = {Source identifier: ofr75544}
}