1. Hages, W. and Nichols, G. (1960) Phys. Rev., 117, pp. 993.
2. Bass, I. and Mieher, R. (1965) Phys. Rev. Lett., 15, pp. 25.
3. RadhaKrishna, S. and Chowdri, B. (1972) Phys. Solidi(a), 14, pp. 11.
4. Neelamegam, P. and Padmanabhan, K. and Selvasekarapandian, S. (1992) Meas. Sci. Technol., 3, pp. 581.
5. Avakian, P. and Smakula, A. (1962) Phys. Rev., 125-5, pp. 1854.