References
- Levelut , A. M. , Germain , C. , Keller , P. , Liebert , L. and Billard , J. 1983 . J. Physique , 44 : 623 – 629 .
- Keller , P. 1984 . Mol. Cryst. Liq. Cryst. , 102 : 295 – 305 .
- Heppke , G. , Kleineberg , P. and Lötzsch , D. 1993 . Liq. Cryst. , 14 : 67 – 71 . and references therein