1. Jaffe H. H. and Orchin M, Theory and Applications of Ultraviolet Spectroscopy (John Wiley and Sons, New York, 1989), pp. 8–9.
2. Brittain E. F. H., George W. O. and Wells C. H. J, Introduction to Molecular Spectroscopy: Theory and Experiment (Academic Press, New York, 1972), p. 68.
3. Quantitative Analysis
4. Banwell C. N., Fundamentals of Molecular Spectroscopy (McGraw-Hill, New York, 1972), 2nd ed., p. 27.