@misc{indiciae96bac9c99655,
  title = {Historical Shoreline Changes in Puerto Rico, 1901-1987},
  author = {E.R. Thieler and W. W. Danforth},
  year = {1993},
  doi = {10.3133/ofr93574},
  url = {https://pubs.usgs.gov/publication/ofr93574},
  note = {Source identifier: ofr93574}
}