Martha W. Evens Ru-Charn Chang Yoon Hee Lee Leemseop Shim Chong-Woo Woo Yuemei Zhang CIRCSIM-Tutor: An Intelligent Tutoring System Using Natural Language Dialogue. 13-14 1997 ANLP http://acl.ldc.upenn.edu/A/A97/A97-2007.pdf db/conf/anlp/anlp1997.html#EvensCLSWZ97