1. E. Schmidt, Czech. J. Phys.,B16, 753 (1966).
2. M. R. Querry, J. Opt. Soc. Amer.,59, 876 (1969).
3. L. N. Latyev, V. A. Petrov, V. Ya. Chekhovskoi, and E. N. Shestakov, Emitting Properties of Solid Materials [in Russian], Énergiya, Moscow (1974).
4. L. N. Latyev, V. Ya. Chekhovskoi, and E. N. Shestakov, Teplofiz. Vys. Temp.,7, 666 (1969).
5. G. A. Korn and T. M. Korn, Mathematical Handbook for Scientists and Engineers, 2nd ed., McGraw-Hill (1967).