Journal of Statistical Physics, Vol. 28, No. 1, 1982, p. 1-41.
The partition-functions-per-site k of several two-dimensional models (notably the eight-vertex, self-dual Potts and hard-hexagon models) can be easily obtained by using an inversion relation for local transfer matrices, together with symmetry and analyticity properties. This technique is discussed, the analyticity properties compared, and some equivalences (and nonequivalences) pointed out.