1. Bayly, E. J. (1968) Spectral analysis of pulse frequency modulation in the nervous system.IEEE Trans. BME-15, 257–265.
2. Coenen, A. J. R. M. (1975) A hardware device for the assessment of fluctuations in heart rate (in Dutch). Ir thesis, Department of Electrical Engineering, Delft University of Technology.
3. Cox, J. R., Fozzard, H., Nolle, F. M. andOliver, G. C. (1969) Some data transformations useful in electrocardiographyin:Stacy &Waxman (Eds.)Computers in biomedical research,3, 181, AC Press, New York.
4. Koenderink, J. J. andvan Doorn, A. J. (1973) Event train decoders with many inputs; pulse density versus momentaneous frequency.Kybernetik 13, 215–222.
5. Lee, Y. W. (1960) Statistical theory of communication. Wiley, New York.