Advances in Information Retrieval : 33rd European Conference on IR Resarch, ECIR 2011, Dublin, Ireland, April 18-21, 2011, Proceedings - Paul Clough, Colum Foley, Cathal Gurrin, Gareth J. F. Jones, Wessel Kraaij, Hyowon Lee, Vanessa Mudoch ((Lecture Notes in Computer Science))