Janina Kotus is Professor of Mathematics at the Warsaw University of Technology, Poland. Her research focuses on dynamical systems, in particular holomorphic dynamical systems. Together with I. N. Baker and Y. Lű she laid the foundations for iteration of meromophic functions. Mariusz Urbański is Professor of Mathematics at the University of North Texas. His research interests include dynamical systems, ergodic theory, fractal geometry, iteration of rational and meromorphic functions, open dynamical systems, iterated function systems, Kleinian groups, diophantine approximations, topology and thermodynamic formalism. He is the author of eight books, seven monographs, and more than 200 papers.