HOPFIELD, J. J. Neurons with graded respomse have collective computational properties like those of two-state neurons. Proc. Natl. Acad. Sci. U. S. A. 1984, 81, 3088-3092
BEHZAD, K. P. On problem solving with Hopfield neural networks. Biol. Cybern. 1990, 62, 415-423