@misc{indiciaec494a1582feb,
  title = {Geologic map of the San Juan Quadrangle, Puerto Rico},
  author = {M. H. Pease and W. H. Monroe},
  year = {1977},
  doi = {10.3133/i1010},
  url = {https://pubs.usgs.gov/publication/i1010},
  note = {Source identifier: i1010}
}