William Klink received his PhD from Johns Hopkins University, USA. He was professor of physics for many years at the University of Iowa, and is now professor emeritus. His main research interests have centered around the study of symmetry, both in its mathematical formulations, and in its physical consequences.Sujeev Wickramasekara received his PhD in theoretical physics from the University of Texas at Austin, USA. He held the Weiss Instructorship in Physics and Astronomy at Rice University before moving to Grinnell College where he is now associate professor of physics. His main research interests include representation theory of groups and its applications to physics, resonance scattering and decay phenomena, and rigged Hilbert spaces.