P. Singer, D. Helic, A. Hotho, and M. Strohmaier. International Conference on World Wide Web, page 1003--1013. Republic and Canton of Geneva, Switzerland, International World Wide Web Conferences Steering Committee, (2015)
K. Pearson, and O. Henrici. Philosophical Transactions of the Royal Society of London. Series A, Containing Papers of a Mathematical or Physical Character, (1896)
A. Noulas, S. Scellato, N. Lathia, and C. Mascolo. Proceedings of the 2012 IEEE 12th International Conference on Data Mining, page 1038--1043. Washington, DC, USA, IEEE Computer Society, (2012)