1. Aerogels, edited by J. Fricke (Springer-Verlag, Berlin, 1985); J. D. LeMay, R. W. Hopper, L. W. Hrubesh, and R. W. Pekala, MRS Bulletin15, 19 (1990).
2. Nuclear Magnetism, Order and Disorder, A. Abragam and M. Goldman (Clarendon Press, 1982);The Superfluid Phase of 3 He, D. Vollhardt and P. Wölfle (Taylor and Francis, 1990).
3. D. T. Sprague,et al. Phys. Rev. Lett.75, 661 (1995).
4. D. T. Sprague,et al., to be published (1996).
5. J. V. Porto and J. M. Parpia, Phys. Rev. Lett.74, 4667 (1995)