Palm, G Former Department Structure and Function of Natural Nerve-Net , Max Planck Institute for Biological Cybernetics, Max Planck Society; Max Planck Institute for Biological Cybernetics, Max Planck Society;
https://link.springer.com/content/pdf/10.1007/BF00336857.pdf (Publisher version)
Palm, G. (1979). On representation and approximation of nonlinear systems Part II: Discrete time. Biological Cybernetics, 34(1), 49-52. doi:10.1007/BF00336857.