Anomalous dispersion of LO phonon branches in Ba0.6K0.4BiO3M. Braden, W. Reichardt, A. S. Ivanov and A. Yu. RumiantsevEurophys. Lett., 34 7 (1996) 531-536DOI: https://doi.org/10.1209/epl/i1996-00490-0
