“…This ring constitutes an important feature of f , and in some sense it provides an "approximation" to interpreting (in (A, B; f )) multiplication of constant elements from N and M by integer variables. It has been used successfully to study different first order theoretic aspects of different types of structures, including rings whose additive group is finitely generated [32], free algebras [22,23,24], and nilpotent groups [33,34]. For us the most important property of R(f ) is that it is e-interpretable in (A, B; f ): Theorem 3.1 (Theorem 3.5 of [16]).…”