1. Weise, E. K., History and Origin, in The Encyclopedia of Spectroscopy ,G. L. Clark, ed., Reinhold, New York, 1960.
2. Harrison, G. R., Lord, R. C., and Loofbourow, J. R., Practical Spectroscopy ,Prentice-Hall, Englewood Cliffs, N. J., 1963.
3. Kirchhoff, G., and Bunsen, R., Chemical Analysis by Means of Spectral Observations (in German), Pogg. Ann. Physik u. Chem. 110, 161 (1860).
4. Gerlach, W., “The Correct Execution and Interpretation of Quantitative Spectrum Analysis” (in German), Z. Anorg. Chem. u í ,383 (1925).
5. Goldschmidt, V. M., and Peters, C. (in German), Nachr. Ges. Wiss. G öttingen, Math. Phys. Klasse ,165, 257 (1931).