1. E B Wilson, J C Decius and P C Cross, Molecular v ibrations (Mc-Graw Hill, New York, 1955)
2. F A Cotton, Chemical applications of group theory (Wiley Eastern Limited, New Delhi, 1974)
3. C J Bradely and A P Cracknell, The mathematical theory of symmetry in solids (Clarendon Press, Oxford, 1972)
4. J S Lomont, Application of finite groups (Academic Press, New York, 1959)
5. C J Bradley, J. Math. Phys. 7, 1145 (1966)