1. Halberg, F., in: Biological Rhythms and Endocrine Function, p. 1 (eds. L.W. Hedlund, J.M. Franz, A.D. Kenny). New York: Plenum 1973
2. Kripke, D.F., in: Advances in Sleep Research, Vol. VI, p. 305 (ed. E.D. Weitzman). New York: Spectrum 1974
3. Richter, C.P.: Quart. Rev. Biol. 2, 307 (1927)
4. Aschoff, J.: Naturwissenschaften 13, 361 (1957)
5. Lal, H., et al., in: Drug Addiction: Experimental Pharmacology, Vol. 1, p. 255. Mount Kisco, New York: Futura 1972