J. Guddat et al.

The Editors: Jürgen Guddat was born in Halle in 1941. Since 1978 he has been ordinary professor of mathematical optimization at Humboldt-University, Berlin, Germany. Ryuichi Hirabayashi was born in Tokyo in 1950. Since 1994 he has been ordinary professor of management science at the Science University of Tokyo, Japan. Hubertus Th. Jongen was born in Oirbeek, The Netherlands in 1947. Since 1987 he has been ordinary professor of mathematics at Aachen University of Technology, Germany. Frank Twilt was born in The Hague in 1942. Since 1984 he has been associate professor of mathematical optimization at the University of Twente, The Netherlands.