1. W. M. Fairbank and G. K. Walters, inProceedings of Symposium on Liquid and Solid 3 He (Ohio State University, 1957).
2. R. L. Garwin and H. A. Reich,Phys. Rev. 115, 1478 (1959).
3. G. Careri, I. Modena, and M. Santini,Nuovo Cimento 13, 1779 (1959).
4. P. Monod and J. A. Cowen, Service di Physique du Solide et Resonance Magnetique, Centre D'Etudes Nucleaires de Saclay, Technical Report (1967), unpublished.
5. D. F. Brewer, D. J. Creswell, T. Goto, M. G. Richards, J. Rolt, and A. L. Thomson, inMonolayer and Submonolayer Helium Films (Proc. Symp. Hoboken, New Jersey, 1973).