1. G. C. Ghirardi, A. Rimini, and T. Weber, ?Unified Dynamics for Microscopic and Macroscopic Systems,?Phys. Rev. D 34, 470 (1986); see alsoPhys. Rev. D 36, 3287 (1987) andFound. Phys. 18, 1 (1988).
2. F. Károlyházy, ?Gravitation and Quantum Mechanics of Macroscopic Bodies,?Magy. Fiz. Foly. 22, 23 (1974) (in Hungarian). The basic ideas of the model have been outlined by Károlyházy inNuovo Cimento 42, 390 (1966). For an (incomplete) presentation of the model see Ref. 5 and A. Frenkel, inQuantum Mechanics?a Half Century Later, J. Leite Lopes and M. Paty. eds., (Reidel, Dordrecht, 1977).
3. E. Joos and H. D. Zeh,Z. Phys. B 59, 223 (1985).
4. W. H. Zurek, inProceedings of the International Symposium Foundations of Quantum Mechanics, S. Kamefuchiet al., eds. (Physical Society of Japan, Tokyo, 1984), p. 181, and references therein.
5. F. Károlyházy, A. Frenkel, and B. Lukács, inPhysics as Natural Philosophy, A. Shimony and H. Feschbach, eds. (MIT Press, Cambridge, Massachusetts, 1982), p. 204, and inQuantum Concepts in Space and Time, R. Penrose and C. J. Isham, eds. (Clarendon Press, Oxford, 1986), p. 109.