Necessary conditions for having wormholes in f(R) gravity
  For a generic $f(R)$ which admits a polynomial expansion of at least third order (i.e. $\frac{d^{3}f}{dR^{3}}\neq 0$) we find the near-throat wormhole solution. Necessary conditions for the existence of wormholes in such $f(R)$ theories are derived for both zero and non-zero matter sources. A particular choice of energy-momentum reveals that the wormhole geometry satisfies the weak energy condition (WEC). For a range of parameters even the strong energy condition (SEC) is shown to be satisfied. 
S. Habib Mazharimousavi and M. Halilsoy
gr-qc