@misc{indiciaea5d895ffbb74,
  title = {Preliminary map of columbium (niobium) and tantalum provinces in the conterminous United States},
  author = {Edwin Wilson Tooker and Raymond Laurence Parker},
  year = {1980},
  doi = {10.3133/ofr79576n},
  url = {https://pubs.usgs.gov/publication/ofr79576N},
  note = {Source identifier: ofr79576N}
}