Ken’ichi Ohshika is a professor of mathematics at Gakushuin University, and a professor emeritus at Osaka University. He received his PhD from the University of Tokyo in 1989, and worked at the Tokyo Institute of Technology, the University of Tokyo, and Osaka University before joining Gakushuin University. His interests include Kleinian groups, hyperbolic geometry, Teichmüller theory, and 3-manifolds. Athanase Papadopoulos is Directeur de Recherche at the French Centre National de la Recherche Scientifique and the University of Strasbourg. He studied at the Ecole Centrale de Paris (engineering diploma in 1983) and at the University of Paris-Sud, Orsay (PhD in mathematics in 1983). He has a large spectrum of interests and has published more than 30 books.