Cubical token systems
  The paper deals with combinatorial and stochastic structures of cubical token systems. A cubical token system is an instance of a token system, which in turn is an instance of a transition system. It is shown that some basic results of combinatorial and stochastic parts of media theory hold almost in identical form for cubical token systems, although some underlying concepts are quite different. A representation theorem for a cubical token system is established asserting that the graph of such a system is cubical. 
Sergei Ovchinnikov