Edwina L. Rissland Kevin D. Ashley Hypotheticals as Heuristic Device. 289-297 1986 conf/aaai/1986-1 AAAI db/conf/aaai/aaai86-1.html#RisslandA86 http://www.aaai.org/Library/AAAI/1986/aaai86-048.php