Note on the Evolution of the Gravitational Potential in Rastall Scalar
  Field Theories
  We investigate the evolution of the gravitational potential in Rastall scalar
field theories. In a single component model a consistent perturbation theory,
formulated in the newtonian gauge, is possible only for $\gamma = 1$, which is
the General Relativity limit. On the other hand, the addition of another
canonical fluid component allows also to consider the case $\gamma \neq 1$.
