1. N. Itoh, Crystal Lattice Defects 3, 115 (1972)
2. M.N. Kabler, in Point Defects in Solids edited by J.H. Crawford and L.N. Slifkin [Plenum Press, N.Y.,1972)
3. T.G. Castner and W. Kanzig, J.Phys.Chem.Solids 3, 17ff (1957)
4. T.D. Woodruff and W. kanzig, ibid, 268 (1958)
5. D. Schoemaker, Phys. Rev. 7B, 786 (1973)