Novel Position-Space Renormalization Group for Bond Directed Percolation   in Two Dimensions
  A new position-space renormalization group approach is investigated for bond directed percolation in two dimensions. The threshold value for the bond occupation probabilities is found to be $p_c=0.6443$. Correlation length exponents on time (parallel) and space (transverse) directions are found to be $\nu_\parallel=1.719$ and $\nu_\perp=1.076$, respectively, which are in very good agreement with the best known series expansion results. 
H. Kaya and A. Erzan