@article {691251,
	title = {Development of in-group favoritism in children{\textquoteright}s third-party punishment of selfishness},
	journal = {Proceedings of the National Academy of Sciences},
	volume = {111},
	year = {2014},
	pages = {12710-12715},
	author = {Warneken, F and Jordan, J and McAuliffe, K}
}
