@misc{indiciaee4a0e66ab116,
  title = {Aeromagnetic map of the Petersham quadrangle, Worcester County, Massachusetts},
  author = {Members of the Engineering Geology and Ground Water Branches, U.S. Geological Survey},
  year = {1970},
  doi = {10.3133/gp699},
  url = {https://pubs.usgs.gov/publication/gp699},
  note = {Source identifier: gp699}
}