Before revision:  We then present a dynamic model of the growth of directed citation networks and show that such systematic disparities in citations can arise from individual preferences to cite authors in the same group (homophily) or the other group (heterophily) , highly cited or active authors (preferential attachment), as well as the size of the group and how frequently new authors join.
After revision:  We present a model for the growth of directed citation networks and show that such systematic disparities in citations can arise from individual preferences to cite authors in the same group (homophily) or the other group (heterophily) , highly cited or active authors (preferential attachment), as well as the size of the group and how frequently new authors join.