1. M. N. Markov, Opt. Spektrosk.,17, No. 6, 934?937 (1964).
2. O. V. Roitsina, Zh. Prikl. Spektrosk.,3, No. 5, 403?409 (1965).
3. G. Gallinaro and R. Vorone, Cryogenics, No. 5, 292?293 (1975).
4. G. Gallinaro, G. Roba, and R. Tatarek, J. Phys. E.,11, No. 7, 628?630 (1978).
5. G. A. Zaitsev and I. A. Khrebtov, Thermal Radiation Detectors [in Russian] (1980), pp. 11?12.