Jennifer Chu-Carroll Krzysztof Czuba John M. Prager Abraham Ittycheriah In Question Answering, Two Heads Are Better Than One. 2003 HLT-NAACL http://acl.ldc.upenn.edu/N/N03/N03-1004.pdf db/conf/naacl/naacl2003.html#Chu-CarrollCPI03