Black holes in scalar-tensor gravity
  Hawking has proven that black holes which are stationary as the endpoint of gravitational collapse in Brans--Dicke theory (without a potential) are no different than in general relativity. We extend this proof to the much more general class of scalar-tensor and f(R) gravity theories, without assuming any symmetries apart from stationarity. 
Thomas P. Sotiriou, Valerio Faraoni
gr-qc astro-ph.HE hep-th