Key points are not available for this paper at this time.
Recently there have been many attempts to evolve one-dimensional two-state cellular automata which classify binary strings according to their densities of 1's and 0's. The current best-known approaches involve particle-based systems of information transfer. A proof is given that there does not exist a two-state cellular automata which performs the task perfectly. This is true even in multiple dimensions.
Land et al. (Mon,) studied this question.