1. J. Rafalowicz, K. Blacerek, B. Sujak, and E. Pega, Phys. Status Solidi (a),4, 779 (1971).
2. R. L. Garwin, Rev. Sci. Instr.,27, 826 (1956).
3. J. Rafalowicz, Acta Phys. Polon.,A42, 169 (1972).
4. G. M. Kondrat'ev, Thermal Measurements [in Russian], Moscow-Leningrad (1957).
5. G. K. White, Experimental Techniques in Low-Temperature Physics [Russian translation], Moscow (1961).