@misc{indiciae1041da1f348d,
  title = {Geology and coal resources of the Durango area, La Plata and Montezuma Counties, Colorado},
  author = {Alfred Dexter Zapp},
  year = {1949},
  doi = {10.3133/om109},
  url = {https://pubs.usgs.gov/publication/om109},
  note = {Source identifier: om109}
}