TY  - RPRT
TI  - Evolution of cooperation by multilevel selection.
AU  - Arne Traulsen
AU  - Martin A Nowak
PY  - 2006
DO  - 10.1073/pnas.0602530103
UR  - https://pubmed.ncbi.nlm.nih.gov/16829575/
ID  - 16829575
ER  -