@misc{indiciaeffb317b60928,
  title = {Metallogenetic eras and periodicity in earth history},
  author = {A.P. Pierce and Ralph Smyser Cannon},
  year = {1969},
  doi = {10.3133/ofr69204},
  url = {https://pubs.usgs.gov/publication/ofr69204},
  note = {Source identifier: ofr69204}
}