Shlomo Havlin is a professor in the Department of Physics at Bar-Ilan University, Israel, where he has also served as the department chairman and Dean of the Faculty of Exact Sciences. Jianxi Gao is a researcher at the Intelligent Information Control Laboratory at Shanghai Jiao Tong University, P.R. China. Amir Bashan is a researcher in the Department of Physics at Bar-Ilan University, Israel.