1. For reviews of earlier work see e.g. various articles in J. de Physique 38—C7 (1977), and [2–5]
2. D. de Fontaine, in: Solid State Physics (ed. by H. Ehrenreich, F. Seitz, and D. Turnbull) Vol. 34, p. 73 (Academic Press, New York 1979).
3. J. Als-Nielsen, in Phase Transitions and Critical Phenomena. vol. 5a (ed. by C. Domb and M. S. Green), p. 88 (Academic Press, New York 1976)
4. A. G. Khachaturyan, Phys. stat. sol. (b) 60, 9 (1973)
5. W. Warlimont (ed.), Order-Disorder Transformations in Alloys (Springer, Berlin-Heidelberg-New York 1974)