1. ε0and ε∞(needed for calculation of vLO and
vTO from R.P. Lowndes and D.H. Martin, Proc. Roy. Soc. Lond., A308, 473, 1969.
2. E. Burstein in Lattice Dynamics, Edited by R.F. Wallis, Pergamon Press, New York, 1965.
3. S.S. Mitra, C. Postmus and J.R. Ferraro, Phys. Rev. Lett., 18, BV502, 1967.
4. J.H. Fertel and C.H. Perry, Phys. Rev., 184, 874, 1969.
5. D.H. Martin, Adv. Phys., 14, 39, 1965.