Preface
Fritz Gesztesy
Baylor University, Waco, USAHarald Hanche-Olsen
The Norwegian University of Science and Technology, Trondheim, NorwayEspen R. Jakobsen
The Norwegian University of Science and Technology (NTNU), Trondheim, NorwayYurii I. Lyubarskii
The Norwegian University of Science and Technology, Trondheim, NorwayNils Henrik Risebro
University of Oslo, NorwayKristian Seip
Norwegian University of Science and Technology, Trondheim, Norway