@misc{indiciae7172586e508b,
  title = {Surficial geology of the Ayer quadrangle, Massachusetts},
  author = {Richard Henry Jahns},
  year = {1953},
  doi = {10.3133/gq21},
  url = {https://pubs.usgs.gov/publication/gq21},
  note = {Source identifier: gq21}
}