Marc B. Vilain Henry A. Kautz Constraint Propagation Algorithms for Temporal Reasoning. 377-382 1986 conf/aaai/1986-1 AAAI db/conf/aaai/aaai86-1.html#VilainK86 http://www.aaai.org/Library/AAAI/1986/aaai86-063.php