Franck Ravat Olivier Teste Ronan Tournier Gilles Zurfluh Top_Keyword: An Aggregation Function for Textual Document OLAP. 55-64 2008 DaWaK http://dx.doi.org/10.1007/978-3-540-85836-2_6 conf/dawak/2008 db/conf/dawak/dawak2008.html#RavatTTZ08