1. Sunta C.M., David M.: PACT 6, 460 (1982).
2. Matsuoka Y., Ikeya M.: Jpn. J. Appl. Phys.34, 6068–6072 (1995)
3. Warashina T., Higashimura T., Maeda Y.: Br. Mus. Occ. Pap.19, 117–128 (1981)
4. Marfunin A.S.: Spectroscopy, Luminescence and Radiation Centers in Minerals. Berlin: Springer-Verlag 1979
5. Schwertmann U.: Iron in Soils and Clay Minerals (Stucki J.W., Goodman B.A., Schwertmann U., eds.), series C, vol. 217. Dordrecht: NATO ASI series 1985.