1. Chandrashekaran, M. K.: Studies on phase-shifts in endogenous rhythms. Z. vergl. Physiol.56, 154?170 (1967).
2. Ehret, C. F.: Discussion on p. 108?109. In: Biochronometry, ed. M. Menaker. Washington, D. C.: National Academy of Sciences 1971.
3. Eskin, A.: Some properties of the system controlling the circadian activity rhythm in sparrows. In: Biochronometry, ed. M. Menaker, p. 55?80. Washington, D. C.: National Academy of Sciences 1971.
4. Johnsson, A., Karlsson, H. G.: A feedback model for biological rhythm. J. theor. Biol.36, 153?194 (1972).
5. Johnsson, A., Karlsson, H. G., Engelmann, W.: Phase shift effects in the kalanchoe petal rhythm due to two or more light pulses. Physiol. Plantarum (Cph.)28, 134?142 (1972).