@misc{indiciae6e4f3582994d,
  title = {Evolution of indirect reciprocity by image scoring.},
  author = {M A Nowak and K Sigmund},
  year = {1998},
  doi = {10.1038/31225},
  url = {https://pubmed.ncbi.nlm.nih.gov/9634232/},
  note = {Source identifier: 9634232}
}