References
- Pietraszko , A. private communication.
- Wolejko , T. , Piskunowicz , P. , Breczewski , T. , Krajewski , T. , Wolejko , T. , Pakulski , G. and Tylczynski , Z. 1987 . materials from the VI-th European Meeting of Ferroelectricity . Sept. 7–11 1987 , Poznan, Poland. to be published in Ferroelectrics, special issue
- Cummins , H. Z. and Levanyuk , A. P. 1983 . Light Scattering Near Phase Transitions Amsterdam, , North-Holland
- Mróz , B. , Kiefte , H. , Clouter , M. J. and Tuszyński , J. A. (1987 . Phys. Rev. B , 36 : 3745
- Aizu , K. 1972 . J. Phys. Soc. Japan , 32 : 1287
- Ahmad , S. F. , Kiefte , H. , Clouter , M. J. and Whitmore , M. D. 1982 . Phys. Rev. B , 26 : 4239
- Landau , L. D. and Lifshitz , E. M. 1959 . Theory of Elasticity , New York : Addison Wesley .
- Ney , J. F. 1957 . Physical Properties of Crystals , Oxford : Clarendon .
- Vacher , R. and Boyer , L. 1972 . Phys. Rev. B , 6 : 639
- Errandonea , G. 1980 . Phys. Rev. B , 21 : 5221
- Toledano , P. , Fejer , M. M. and Auld , B. A. 1983 . Phys. Rev. B , 27 : 5717
- This is supported by the recent studies of Krajewski who found the LRSHS not optically active, which excludes point group 4 as a prototype symmetry.