@misc{indiciae720ac952b855,
  title = {The occurrence of columbium and tantalum},
  author = {Michael Fleischer and James O. Harder},
  year = {1945},
  doi = {10.3133/tei14},
  url = {https://pubs.usgs.gov/publication/tei14},
  note = {Source identifier: tei14}
}