Recent advances and open challenges in percolation N. Araújo, P. Grassberger, B. Kahng, K.J. Schrenk and R.M. Ziff Eur. Phys. J. Special Topics, 223 11 (2014) 2307-2321 Published online: 24 October 2014 DOI: 10.1140/epjst/e2014-02266-y