Sofia Stamou Dimitris Christodoulakis Retrieval Efficiency of Normalized Query Expansion. 604-607 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3406&spage=604 2005 conf/cicling/2005 CICLing db/conf/cicling/cicling2005.html#StamouC05