@article{small,
  title={On the experimental silicification of microorganisms II. On the time of appearance of eukaryotic organisms in the fossil record},
  author={S Francis, L Margulis, E S Barghoorn},
  journal={Precambrian Research},
  volume={6},
  pages={65-100},
  year={1978},
  doi={https://doi.org/10.1016/0301-9268(78)90055-4}
}