Advances in Information Retrieval Theory Second International Conference on the Theory of Information Retrieval, ICTIR 2009 Cambridge, UK, September 10-12, 2009 Proceedings - Azzopardi, Leif; Kazai, Gabriella; Robertson, Stephen; Rüger, Stefan; Shokouhi, Milad; Song, Dawei; Yilmaz, Emine (Springer Berlin Heidelberg : Imprint: Springer, 2009)