@Inproceedings{grahl2007clustering,
  author = {Grahl, Miranda and Hotho, Andreas and Stumme, Gerd},
  title  = {Conceptual Clustering of Social Bookmarking Sites},

  year   = {2007},
  number = {},
  url    = {},

  const  = {\ text}
}
@Techreport{citeulike:739394,
  author = {Heymann, Paul and Garcia-Molina, Hector},
  title  = {Collaborative Creation of Communal Hierarchical Taxonomies in Social Tagging Systems},

  year   = {2006},
  number = {2006-10},
  url    = {http://dbpubs.stanford.edu:8090/pub/2006-10},

  const  = {\ text}
}