1. Structural Complexity I;Balcázar,1988
2. J. Culberson, Sokoban is PSPACE-complete, in: Internat. Conf. on Fun with Algorithms, Proc. in Informatics 4, Carleton Scientific, Waterloo, Canada, Elba, Italy, 1999, pp. 65–76.
3. E.D. Demaine, M.L. Demaine, J. O'Rourke, PushPush and Push-1 are NP-hard in 2D, in: Proc. 12th Annual Canadian Conf. on Computational Geometry, Fredericton, New Brunswick, Canada, 2000, pp. 17–20.
4. Sokoban and other motion planning problems;Dor;Comput. Geom. Theory Appl.,1999
5. RushHour is PSPACE-complete, or Why you should generously tip parking lot attendants;Flake;Theoret. Comput. Sci.,2002