緑髭効果
C., et al. (2003) Single-gene greenbeard effects in the social amoeba Dictyostelid|Dictyostelium discoideum. Science, 299, 105-106. Link
Green Beard Ethnic Nepotism? on-line discussion about the topic by various authors, December 22, 2004, accessed Jan 2008
Grafen, Alan Green beard as death warrant 1998, Nature, accessed Jan 2008 - short discussion and critique on the possible existence of a green beard gene