@article{MichaelisN17,
  title = {Propositional Proof Systems},
  author = {Julius Michaelis and Tobias Nipkow},
  year = {2017},
  url = {https://www.isa-afp.org/entries/Propositional_Proof_Systems.shtml},
  researchr = {https://researchr.org/publication/MichaelisN17},
  cites = {0},
  citedby = {0},
  journal = {Archive of Formal Proofs},
  volume = {2017},
}