6Levine S S, Kurzban R. Explaining clustering in social networks :Towards an evolutionary theory of cascading benefits. Managerial and Decision Economics,2006,27 (2 - 3 ) : 173 - 187.
7Thelwall M. Homophily in MySpace. Journal of the American Society for Information Science and Technology, 2009, 60(2) :219 - 231.