@misc{indiciaed3fbceb4c652,
  title = {Geologic map of the San German quadrangle, Puerto Rico},
  author = {Richard P. Volckmann},
  year = {1977},
  doi = {10.3133/ofr77182},
  url = {https://pubs.usgs.gov/publication/ofr77182},
  note = {Source identifier: ofr77182}
}