Alexandros Nanopoulos Hans-Henning Gabriel Myra Spiliopoulou Spectral Clustering in Social-Tagging Systems. 87-100 2009 WISE http://dx.doi.org/10.1007/978-3-642-04409-0_15 conf/wise/2009 db/conf/wise/wise2009.html#NanopoulosGS09