A generalization of Cobham's Theorem
  If a non-periodic sequence $X$ is the image by a morphism of a fixed point of both a primitive substitution $\sigma$ and a primitive substitution $\tau$, then the dominant eigenvalues of the matrices of $\sigma$ and of $\tau$ are multiplicatively dependent. This is the way we propose to generalize Cobham's Theorem. 
Fabien Durand (LAMFA)