1. Maintaining Knowledge about Temporal Intervals;Allen,1983
2. Towards a General Theory of Action and Time;Allen;Artif. Intell.,1984
3. Negation as Failure;Clark,1978
4. Formal Semantics for Time in Databases;Clifford;ACM Trans. Database Systems,1983
5. Abduction Compared with Negation by Failure;Eshghi,1989