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\bibitem{Lang_etal1991} Lang, P. T., Leipold, I., Knott, W. J., Semenov, A. D., Gol{\textquoteright}tsman, G. N., \& Renk, K. F. (1991). New far-infrared laser lines from CH3Cl and CH3Br optically pumped with a continuously tunable high pressure CO2 laser. \textit{Appl. Phys. B}, \textit{53}(4), 207--212.

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