Peter M. Wiemer-Hastings Katja Wiemer-Hastings Arthur C. Graesser Approximate Natural Language Understanding for an Intelligent Tutor. 192-196 1999 conf/flairs/1999 FLAIRS Conference db/conf/flairs/flairs1999.html#Wiemer-HastingsWG99 http://www.aaai.org/Library/FLAIRS/1999/flairs99-034.php