1. Rushbrooke, G.S. and Morgan, D.J. (1961) Mol. Phys., 4, pp. 1 - 1.
2. Behringer, R.E. (1957) J. chem. Phys., 26, pp. 1504 - 1504.
3. Rushbrooke, G.S. and Wood, P.J. (1958) Mol. Phys., 1, pp. 257 - 257.
4. Domb, C. and Sykes, M.F. (1957) Proc. roy. Soc. A, 240, pp. 214 - 214.
5. Rushbrooke, G.S. and Wood, P.J. (1955) Proc. phys. Soc., Lond. A, 68, pp. 1161 - 1161.