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2. S. E. Frish, Optical Atomic Spectra [in Russian], Fizmatgiz, Moscow-Leningrad (1963).
3. E. Jahnke and F. Emde, Tables of Functions with Formulas and Curves, 4th ed., Dover.
4. A. A. Kharkevich, Spectra and Their Analysis [in Russian], Gostekhizdat, Moscow (1953).
5. B. J. Witteman, ?Inversion mechanisms, population densities, and coupling-out of a high-power molecular laser,? Phillips Res. Repts., 21, No. 2 (1966).