conf/sigmod/91 Douglas B. Lenat Computers versus Common Sense. 1 1991 SIGMOD Conference db/conf/sigmod/sigmod91.html#Lenat91 http://doi.acm.org/10.1145/115790.277951 db/conf/sigmod/Lenat91.html SIGMOD91/P001.PDF journals/cacm/LenatGPPS90