@misc{indiciaef314175647c8,
  title = {Large-magnitude Middle Ordovician volcanic ash falls in North America and Europe: Dimensions, emplacement and post-emplacement characteristics},
  author = {W.D. Huff and Dennis R. Kolata and Stig M. Bergstrom and Y.-S. Zhang},
  year = {1996},
  url = {https://pubs.usgs.gov/publication/70018055},
  note = {Source identifier: 70018055}
}