The dynamics of critical Kauffman networks under asynchronous stochastic   update
  We show that the mean number of attractors in a critical Boolean network under asynchronous stochastic update grows like a power law and that the mean size of the attractors increases as a stretched exponential with the system size. This is in strong contrast to the synchronous case, where the number of attractors grows faster than any power law. 
Florian Greil and Barbara Drossel