1. Padden, F.J., and Keith, H.D., (1959), J. Appl. Phys., 30, 1479.
2. Geil, P.H., (1960), J. Polym. Sci, 47, 63.
3. Keller, A., (1955), J. Polym. Sci, 17, 291.
4. Sears, G. W., (1961), J. Phys.Chem., 65, 1738.
5. Alley, R.H., and Basset, D.C., (1982), Polymer, 27, 17077.