"Polarized Raman spectra of tetragonal BaTi03 have been obtained at room temperature … [excitation laser 633 nm] … Using several different crystallographic directions for the phonon wave vector q, most of the vibrational modes for q ~ 0 have been classified using Raman data alone. Three pairs of longitudinal transverse A1 modes have been observed with frequencies which semiquantitatively satisfy the Lyddane Sachs-Teller relationship. A low-frequency transverse E mode has been observed at 10 cm -1 and assigned to the ferroelectric soft-mode system. The soft-mode result has been discussed in terms of the effect of damping on the dispersion relation" .