@misc{indiciaec2ac3aa4f20f,
  title = {Cretaceous and lower Tertiary stratigraphy of the Gurabo and El Yunque quadrangles, Puerto Rico},
  author = {Victor M. Seiders},
  year = {1971},
  doi = {10.3133/b1294f},
  url = {https://pubs.usgs.gov/publication/b1294F},
  note = {Source identifier: b1294F}
}