1. W. Kundig and R.S. Hargrove, Solid State Commun. 7, 223 (1969).
2. B.J. Evans and S.S. Hafner, J. Appl. Phys., 40, 1411 (1969).
3. B.J. Evans, 17th AIP Conference on Magnetism and Magnetic Materials, Paper No. 1C-3, Nov. (1971).
4. R.S. Hargrove and W. Kundig, Solid State Commun. 8, 303 (1970).
5. M.B. Robin and P. Day, “Advances in Inorganic Chemistry and Radiochemistry”, 10, 294 (1966) Academic Press (New York).