@article{anormknockoutmethodonindirect,
  title = {A norm knockout method on indirect reciprocity to reveal indispensable norms},
  author = {Hitoshi Yamamoto and Isamu Okada and Satoshi Uchida and Tatsuya Sasaki},
  year = {2017},
  eprint = {1703.03943},
  archivePrefix = {arXiv},
  url = {http://arxiv.org/abs/1703.03943v1},
}