@misc{indiciaec5649535e311,
  title = {Plant microfossil record of the terminal cretaceous event in the western United States and Canada},
  author = {Douglas J. Nichols and R. Farley Fleming},
  year = {1990},
  doi = {10.1130/spe247-p445},
  url = {https://pubs.usgs.gov/publication/70221504},
  note = {Source identifier: 70221504}
}