1. Schaub-Shaver, J.A., Stauffer, A.D.: J. Phys. B13, 1457 (1980)
2. Geltman, S.: J. Phys. B4, 1288 (1971)
3. Winters, K.H.: Ph. D. Thesis, University of Durham (1974)
4. Scott, T., McDowell, M.R.C.: J. Phys. B8, 1851 (1975)
5. Baluja, K.L., McDowell, M.R.C.: J. Phys. B12, 835 (1979)