A Unified Theory of Heuristic Evaluation Functions and its Application to Learning. - Jens Christensen 001; Richard E. Korf (AAAI, 1986)

A Hierarchical Planner that Generates Its Own Hierarchies. - Jens Christensen 001 (AAAI, 1990)

A Formal Model for Classical Planning. - Jens Christensen 001; Adam J. Grove (IJCAI, 1991)