@misc{indiciae06f0cca60232,
  title = {Geologic map of the Arecibo quadrangle, Puerto Rico},
  author = {R. P. Briggs},
  year = {1968},
  doi = {10.3133/i551},
  url = {https://pubs.usgs.gov/publication/i551},
  note = {Source identifier: i551}
}