Bertil Gustafsson, PHD, is Professor Emeritus in the Department of Information Technology at Uppsala University and is well known for his work in initial-boundary value problems. Heinz-Otto Kreiss, PHD, is Professor Emeritus in the Department of Mathematics at University of California, Los Angeles and is a renowned mathematician in the field of applied mathematics. Joseph Oliger, PHD, was Professor in the Department of Computer Science at Stanford University and was well known for his early research in numerical methods for partial differential equations.