Mailing address: Maarten H. van Emden Department of Computer Science University of Victoria P.O. Box 3055, Victoria, B.C. V8W 3P6 Canada For courier delivery: Department of Computer Science University of Victoria 3800 Finnerty Road Victoria, B.C. V8P 5C2 Canada Campus location: ECS 627 fax: (250) 472-5708 E-mail: before the at-sign: vanemden after the at-sign: cs.uvic.ca