@misc{indiciae58c04066cbc5,
  title = {Carbonatites of the world, explored deposits of Nb and REE— Database and grade and tonnage models},
  author = {Vladimir I. Berger and Donald A. Singer and Greta J. Orris},
  year = {2009},
  doi = {10.3133/ofr20091139},
  url = {https://pubs.usgs.gov/publication/ofr20091139},
  note = {Source identifier: ofr20091139}
}