Attended a literature review on Question Answering by Akihiro Katsura. Some interesting references.

• Green, Chomsky, et al. 1961. The BASEBALL system.
• rule-based
• Isozaki et al. 2009.
• machine learning-based
• Methodology of QA
• Question analysis
• Xue et al. SIGIR 2008. Retrieval  models for QA archives.
• Text retrieval
• Jones et al. IPM 2000. ---Okapi/BM25
• Berger et al. SIGIR 2000.---Bridging the lexical chasm (OOV problem)
• Brill et al. TREC 2001.---Data intensive QA
• Answer candidate extraction
• Lafferty et al. ICML 2001.---CRF
• Ravichandran & Hovy. ACL 2002.---Surface text patterns for QA
• Answer selection
• Clarke et al. SIGIR 2001.---Redundancy in QA
• Other related work
• Cao et al. WWW 2008.---Recommending questions
• Wang et al. SIGIR 2009.---Similar questions
• Wang et al. SIGIR 2009.---answer ranking
• Jeon et al. SIGIR 2006.---answer ranking with non-textual features (votes, etc.)