1. Matthews, S.W.: Readers Digest Mai 1977, S. 39 (National Geographic, Nov. 1976)
2. Flohn, H.: Naturwissenschaften 66, 325 (1979)
3. Olsen, L.F., Degn, H.: Nature 267, 177 (1977)
4. Bullard, E., in: AIP Conf. Proc., La Jolla Inst., Ed. Siebe Jorna, Topics in Nonlinear Dynamics, AIP, 1978, p. 373
5. Ahlers, G., in: Fluctuations, Instabilities, and Phase Transitions, p. 181. Proc. Geilo Conf. (ed. Riste, T.). New York: Plenum 1976