Cosmological Dynamics of Fourth-Order Gravity with a Gauss-Bonnet Term

We consider the cosmological dynamics of fourth-order gravity with both f(R) and Phi(G) corrections to the Einstein gravity (G is the Gauss-Bonnet invariant). The particular case for which both terms are equally important on power-law solutions is described. These solutions and their stability are studied using the dynamic system approach. We also discuss the condition of existence and stability of a de Sitter solution in a more general situation of power-law f and Phi.