1. Gaydon, A. G., and Pearse, R. W. B., Identification of Molecular Spectra.
2. Hertenstein, H., Z. wiss. Phot, 11, 69, 119 (1912).
3. Coheur, F., and Rosen, B., Bull. Soc. Roy. Sci. Liége, 405 (1941).
4. Rosen, B., Bull. Soc. Roy. Sci. Liége, 176 (1944).