1. L. E. Orgel, An Introduction to Transition-Metal Chemistry: Ligand Field Theory, Wiley, NY (1966).
2. N. A. Kostromina, V. N. Kumok, and N. A. Skorik, Chemistry of Coordination Compounds [in Russian], Vyssh. Shkola, Moscow (1990).
3. S. V. Vonsovskii, S. V. Grum-Grzhimailo, V. I. Cherepanov, et al., Crystal Field Theory and Optical Spectra of Impurity Ions with an Unfilled d Shell [in Russian], Nauka, Moscow (1969).
4. T. Bates, “Ligand field theory and absorption spectra glasses of transition metal ions in glasses, ” in: Modern Aspects Vitreous State, 2, 166–174 (1962).
5. C. Bamford, “Application of ligand field theory to coloured glass,” Phys. Chem. Glasses, 3(5), 141–156 (1962).