The Holography Hypothesis and Pre-Big Bang Cosmology
  The consequences of holography hypothesis are investigated for the Pre-big-bang string cosmological models. The evolution equations are obtained from the tree level string effective action. It is shown that $S/A$ is bounded by a constant in each case, $S$ being the entropy within the volume bounded by the horizon of area $A$. 
A. K. Biswas, J. Maharana and R. K. Pradhan