@misc{indiciaeeb9866b91c9b,
  title = {Preliminary geologic map of the Humacao quadrangle, Puerto Rico},
  author = {John W. M’Gonigle},
  year = {1976},
  doi = {10.3133/ofr76126},
  url = {https://pubs.usgs.gov/publication/ofr76126},
  note = {Source identifier: ofr76126}
}