1. Chemistry of the Earth's Crust 1964
2. CLARK, S.P., ABSORPTION SPECTRA OF SOME SILICATES IN THE VISIBLE AND NEAR INFRARED, AMERICAN MINERALOGIST 42: 732 (1957).
3. Dunitz, J. D., Journal of Physics and Chemistry of Solids 3: 318 (1957).
4. GOLDSCHMIDT, V. M., JOURNAL OF THE CHEMICAL SOCIETY: 655 (1937).
5. Jorgensen, C., Absorption Spectra and Chemical Bonding in Complexes: 296 (1962).