@misc{indiciae583441a8e844,
  title = {Summary of mineral resources in four selected areas of Colombia},
  author = {Charles MaFarland Tschanz and R.B. Hall and T. Feininger and D.E. Ward and R. Goldsmith and D.H. MacLaughlin and E. Maughan},
  year = {1968},
  doi = {10.3133/ofr68279},
  url = {https://pubs.usgs.gov/publication/ofr68279},
  note = {Source identifier: ofr68279}
}