1. E. Murad and J.H. Johnston, in:Mössbauer Spectroscopy Applied to Inorganic Chemistry, Vol. 2, ed. G.J. Long (Plenum Press, New York, 1987) p. 507.
2. JCPDS Index Card No. 20-713.
3. C.D. Wagner, W.M. Riggs, L.E. Davis, G.F. Moulder and G.E. Muilemberg, eds.,Handbook of X-ray Photoelectron Spectroscopy (Perkin Elmer, Minnesota) p. 76.
4. K.J. Gallagher and D.N. Phillips, Chimia 23 (1969) 465.
5. Y. Ujihira, A. Handa and M. Fujinami, in:Industrial Applications of the Mössbauer Effects, eds. G.J. Long and J.G. Stevens (Plenum Press, New York, 1986) p. 315.