1. E. Ising: 1925. Z. Physik 31, 253. For a more recent treatment, see B. M. McCoy and T. T. Wu: 1973. The Two-dimensional Ising Model. Harvard University Press, Cambridge, Mass.
2. L. Onsager: 1944. Phys. Rev. 65, 117 and L. Onsager: 1949. Nuovo Cim. 6, (Suppl.) 261.
3. C. N. Yang and T. D. Lee: 1952 Phys. Rev. 87, 404 and T. D. Lee and C. N. Yang: 1952. Phys. Rev. 87, 410.
4. See, e.g., K. G. Wilson: 1975. Rev. Mod. Phys. 47C, 773; D. J. Amit: 1984. Field Theory, the Renormalization Group and Critical Phenomena. World Scientific, Singapore; J. Zinn-Justin: 1989. Quantum Field Theory and Critical Phenomena. Oxford University Press, Oxford.
5. D. Mukamel: 2000. In: M. R. Evans and M. E. Cates (eds.) Soft and Fragile Matter: Nonequilibrium Dynamics, Metastability and Flow. Scottish Universities Summer School in Physics, Edinburgh; cond-mat/0003424.