1. P. C. Hohenberg and B. I. Halperin, Rev. Mod. Phys. 49, 435 (1977).
2. J. V. Sengers, in Proceedings of the 1980 Cargése Summer Institute on Phase Transitions, M. Levy, J. C. Le Guillou, and J. Zinn-Justin (eds.), (Plenum Publ. Corp.) to be published.
3. G. Ahlers, in Ref. 2; and in: Quantum Liquids, J. Ruvalds and T. Regge, eds. (North Holland, Amsterdam, 1978). Note that there remains the problem of the pressure dependence of the free energy per correlation volume which the theory predicts to be universal.
4. R. A. Ferrell, N. Menyhard, H. Schmidt, F. Schwabl and P. Szépfalusy, Ann. Phys. (N. Y.) 47, 565 (1968).
5. B. I. Halperin, and P. C. Hohenberg, Phys. Rev. 177, 952 (1969).