1. C. H. Bennett, inEmerging Syntheses in Science (Santa Fe Institute, Santa Fe, New Mexico, 1985), David Pines, ed., pp. 297–313. See also unpublished manuscript “On the Logical Depth of Sequences and their Reducibilities to Random Sequences” (1982). The first published description of logical depth is by G. Chaitin,I.B.M. J. Res. Develop. 21, 350–359 (1977).
2. C. H. Bennett and G. Grinstein,Phys. Rev. Lett. 55, 657–660 (1985).
3. E. Domany and W. Kinzel,Phys. Rev. Lett. 53, 311 (1985).
4. E. Fredkin and T. Toffoli,Internat. J. Theor. Phys. 21, 219 (1982).
5. P. Gacs, Technical Report No. 132, Computer Science Dept. University of Rochester, 1983, to appear inJ. Comp. Sys. Sc.