1. Shaller, W.T.: Am. Mineral. 8 (1923) 93.
2. Slawson, C.B.: Am. Mineral. 10 (1925) 305.
3. Wyart, J.: Bull. Soc. Fr. Mineral. Cristallogr. 56 (1933) 81.
4. Tiselius, A.: Z. Phys. Chem. Abt. A 169 (1934) 425.
5. Herzeberg, G.: Molecular Spectra and Molecular Structure, II; Infrared and Raman Spectra of Polyatomic Molecules, D, Princeton, New Jersey: Van Nostrand Comp., 1945.