Kazunori Komatani Satoshi Ikeda Yuichiro Fukubayashi Tetsuya Ogata Hiroshi G. Okuno Ranking Help Message Candidates Based on Robust Grammar Verification Results and Utterance History in Spoken Dialogue Systems. 314-321 2009 SIGDIAL Conference http://www.aclweb.org/anthology/W09-3946 conf/sigdial/2009 db/conf/sigdial/sigdial2009.html#KomataniIFOO09