1. Allnatt, A.R.,and Jacobs, P.W.M., 1961, Proc. Roy. Soc. A260, 350.
2. Allnatt, A.R., and Loftus, E., 1973a, J. Chem. Phys., 59, 2541.
3. Allnatt, A.R., and Loftus E., 1973b, J. Chem. Phys., 59, 2550.
4. Allnatt, A.R., and Yuen, P.S., 1975e, J. Phys.C., 8, 2199.
5. Allnatt, A.R., and Yuen, Y.S., 1975b, J. Phys. C., 8, 2213.