“…First suppose that (A, /) is a subshift of finite type (see [13]). Then the theorem can be proved by the "transfer matrix" method of statistical mechanics (see [7], [1], [12], [9], [10]). The general case reduces to that one: using a Markov partition for A (see [11], [2]) one can, by a combinatorial lemma of Manning [6], write where K m consists of the f periodic points of prime period m. [5] ).…”