@misc{indiciaebcf1a518333f,
  title = {Precambrian deposits of zinc-copper-lead sulfides and zinc spinel (gahnite) in Colorado},
  author = {Douglas M. Sheridan and William H. Raymond},
  year = {1984},
  doi = {10.3133/b1550},
  url = {https://pubs.usgs.gov/publication/b1550},
  note = {Source identifier: b1550}
}