Ulrik Brandes Daniel Delling Marco Gaertler Robert Görke Martin Hoefer Zoran Nikoloski Dorothea Wagner On Modularity Clustering. 172-188 2008 20 IEEE Trans. Knowl. Data Eng. 2 http://doi.ieeecomputersociety.org/10.1109/TKDE.2007.190689 db/journals/tkde/tkde20.html#BrandesDGGHNW08