1. M. J. Lea and P. W. Retz,Physica 107B, 223 (1981).
2. S. J. Putterman,Superfluid Hydrodynamics (North-Holland, Amsterdam, 1974).
3. L. C. Yang, Ph.D. Thesis, University of California at Los Angeles (1973).
4. A. P. Borovikov,Prib. Tekh. Eksp. 19, 184 (1976) (Instrum. Expt. Tech. (USSR),19, 223 (1976).
5. P. R. Roach and J. B. Ketterson,Phys. Rev. Lett. 36, 736 (1976);J. Low Temp. Phys. 25, 637 (1976).