@misc{indiciaeeebc9bdce910,
  title = {Evolution of indirect reciprocity.},
  author = {Martin A Nowak and Karl Sigmund},
  year = {2005},
  doi = {10.1038/nature04131},
  url = {https://pubmed.ncbi.nlm.nih.gov/16251955/},
  note = {Source identifier: 16251955}
}