Exponents and for preferential creation and preferential attachment.

Exponents and as in , which characterize the influence of current degree of activity and degree of popularity on the formation of cross links between existing users and existing items as well as the formation of cross links between existing users (items) and new items (user) [in the brackets] The results are averaged over 10 randomly selected snapshots, where the exponents are determined by least-square fitting, and generally.