@misc{indiciaebfd33ad7b015,
  title = {Geologic map of the San Sebastian Quadrangle, Puerto Rico},
  author = {O. T. Tobisch and M.D. Turner},
  year = {1971},
  doi = {10.3133/i661},
  url = {https://pubs.usgs.gov/publication/i661},
  note = {Source identifier: i661}
}