Brown, L. R., J. S. Margolis, J. P. Champion, J. C. Hilico, M. Loete, C. Chackerian, G. Tarrago, and D. C. Benner (1992), Methane and its Isotopes: Current Status and Prospects for Improvement, J Quant. Spectrosc. Radiat. Trans., 48, 617-628.