Robert E. Wray III John E. Laird Randolph M. Jones Compilation of Non-Contemporaneous Constraints. 771-778 1996 conf/aaai/1996-1 AAAI/IAAI, Vol. 1 db/conf/aaai/aaai96-1.html#WrayLJ96 http://www.aaai.org/Library/AAAI/1996/aaai96-115.php