Kujawski, Bernard, Janusz Hołyst, and Geoff J. Rodgers. "Growing trees in internet news groups and forums." Physical Review E—Statistical, Nonlinear, and Soft Matter Physics 76.3 (2007): 036103.

This empirical study examines the network structures formed by users in internet news groups and forums, revealing that they organize into scale-free trees influenced by discussion topics. Specialist topics tend to have short, shallow tree structures, while universal topics result in deeper trees. The analysis of response times shows a composite power-law distribution, indicating differences in moderation presence. Activity correlation functions reflect users' daily routines, and the distance distribution between messages and their roots varies, being exponential in news groups and power-law in forums. Notably, a linear relationship between supremacy and degree contrasts with traditional Barabási-Albert network models.