Substitutions for tilings $\{p,q\}$
  In this paper we consider tiling $\{p, q \}$ of the Euclidean space and of the hyperbolic space, and its dual graph $\Gamma_{q, p}$ from a combinatorial point of view. A substitution $\sigma_{q, p}$ on an appropriate finite alphabet is constructed. The homogeneity of graph $\Gamma_{q, p}$ and its generation function are the basic tools for the construction. The tree associated with substitution $\sigma_{q, p}$ is a spanning tree of graph $\Gamma_{q, p}$. Let $u_n$ be the number of tiles of tiling $\{p, q \}$ of generation $n$. The characteristic polynomial of the transition matrix of substitution $\sigma_{q, p}$ is a characteristic polynomial of a linear recurrence. The sequence $(u_n)_{n \geq 0}$ is a solution of this recurrence. The growth of sequence $(u_n)_{n \geq 0}$ is given by the dominant root of the characteristic polynomial. 
Maurice Margenstern, Guentcho Skordev