@misc{indiciae4ab3d5cbb1d8,
  title = {Geologic map of the Ponce Quadrangle, Puerto Rico},
  author = {R.D. Krushensky and W. H. Monroe},
  year = {1975},
  doi = {10.3133/i863},
  url = {https://pubs.usgs.gov/publication/i863},
  note = {Source identifier: i863}
}