K. Chen, R. Lu, C. Wong, G. Sun, L. Heck, and B. Tseng. CIKM '08: Proceeding of the 17th ACM conference on Information and knowledge management, page 1143--1152. New York, NY, USA, ACM, (2008)
S. Maslov, and S. Redner. (2009)cite arxiv:0901.2640
Comment: 3 pages, 1 figure, invited comment for the Journal of Neuroscience.
The arxiv version is microscopically different from the published version.