1. A. Farcas Orthohydrogen Parahydrogen and Heavy Hydrogen (Cambridge Univ. Press Cambridge 1935).
2. Konyukhov V. K., Tikhonov V. I., Tikhonova T. L., Bull. Lebedev Phys. Inst. N.9, 12 (1988).
3. Details of the experimental method and spectral analysis are available on Science Online.
4. Volkov A. A., et al., Infrared Phys. 25, 369 (1985).
5. Meiboom S., J. Chem. Phys. 34, 375 (1961).