@misc{indiciae50bc3b43457e,
  title = {Geologic map of the Barceloneta quadrangle, Puerto Rico},
  author = {R. P. Briggs},
  year = {1965},
  doi = {10.3133/i421},
  url = {https://pubs.usgs.gov/publication/i421},
  note = {Source identifier: i421}
}