PDF] PushPush-k is PSPACE-Complete
A Survey Of NP-Complete Puzzles
Pushing Blocks (Erik Demaine)
PDF] PushPush and Push-1 are NP-hard in 2D
PDF) Particle Computation: Designing Worlds to Control Robot
Curriculum Vitæ - Erik Demaine
CSCI 4341
PDF] Push-2-f is pspace-complete
PDF] PushPush-k is PSPACE-Complete