1. White, G. K., Experimental Techniques in Low-Temperature Physics, 2nd ed., Oxford University Press (Clarendon Press) (1968).
2. Hoare, F. E., Jackson, L. C, and Kurti, N., (eds.) Experimental Cryophysics, Butterworths, London (1961), Chapter 9.
3. Powell, R. L., Caywood, L. P., Bunch, M. D., Temperature
3 (Part 2), 65 (1962).
4. National Bureau of Standards Circular 561 (1955).
5. Croft, A. J., Cryogenics
4, 143 (1964).