@misc{indiciaecf38273bea0e,
  title = {Mineral resources of Colombia (other than petroleum)},
  author = {Quentin Dreyer Singewald},
  year = {1950},
  doi = {10.3133/b964b},
  url = {https://pubs.usgs.gov/publication/b964B},
  note = {Source identifier: b964B}
}