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 $\gamma \neq 1$. 
J. C. Fabris, M. Hamani Daouda, O. F. Piattella
astro-ph.CO gr-qc