Boris Katz Gregory Marton Gary C. Borchardt Alexis Brownell Sue Felshin Daniel Loreto Jesse Louis-Rosenberg Ben Lu Federico Mora Stephan Stiller Özlem Uzuner Angela Wilcox External Knowledge Sources for Question Answering. 2005 TREC http://trec.nist.gov/pubs/trec14/papers/mit-katz.qa.pdf conf/trec/2005 db/conf/trec/trec2005.html#KatzMBBFLLLMSUW05