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2. R. L. Stratonovich: Topics in the Theory of Random Noise, Vol. II (Gordon and Breach, New York 1967) Chap. 9
3. A. J. Viterbi: Proc. IEEE 51, 1737 (1963)
4. A. J. Viterbi: Principles of Coherent Communication (McGraw-Hill, New York 1966)
5. W. C. Lindsey: Synchronization Systems in Communication and Control (Prentice Hall, Englewood Cliffs, NJ 1972)