1. Wexler, A., J. Appl. Phys.
22, 1463 (1951);
2. Wexler, A., and Jacket, H. S., Rev. Sci. Instr.
22, 282 (1951).
3. White, G. K., Experimental Techniques in Low-Temperature Physics, 2nd ed., Oxford University Press (Clarendon Press) (1968), p.211.
4. Daunt, J. C., and Johnston, H. L., Rev. Sci. Instr.
20, 122 (1949).
5. Croft, A. J., and Jones, G. O., Brit. J. Appl. Phys., 1, 137 (1950).