1. Burns G R 1968Inorg. Chem.
7 277
2. Campbell M J and Grazeskowiak R 1968J. Inorg. Nucl. Chem.
30 1865
3. Campbell M J, Grazeskowiak R and Thomas R 1976Spectrochim. Acta
A32 556
4. Chandra S, Pandeya K B, Sindhwani S K and Singh R P 1980Gazz. Chim. Italia
110 207
5. Dyer J R 1974Application of absorption spectroscopy of organic compounds (New Delhi: Prentice Hall) p. 40