@article{Fuchs2011SettheoreticG,
  title={Set-theoretic geology},
  author={Gunter Fuchs and Joel David Hamkins and Jonas Reitz},
  journal={Ann. Pure Appl. Log.},
  year={2011},
  volume={166},
  pages={464-501},
  url={https://api.semanticscholar.org/CorpusID:36896921}
}