On the existence of singularity-free solutions in quartic gravity
  We study a general field theory of a scalar field coupled to gravitation through a quadratic Gauss-Bonnet term $\xi({\phi})$$R_{GB}^2$. We show that, under mild assumptions about the function $\xi(\phi)$, the classical solutions in a spatially flat FRW background include singularity - free solutions. 
J.Rizos and K. Tamvakis