@misc{indiciae1fc8e00a5f4d,
  title = {Geochemistry of niobium and tantalum},
  author = {Raymond Laurence Parker and Michael Fleischer},
  year = {1968},
  doi = {10.3133/pp612},
  url = {https://pubs.usgs.gov/publication/pp612},
  note = {Source identifier: pp612}
}