Operations Research '91

th The purpose of this volume is to reflect the scientific activities during the 16 Sym- posium on Operations Research which took place at the University of Trier from September 9 through September 11, 1991. The Symposia on Operations Research are the annual conferences of the Gesellschaft fur Mathematik, Okonomie und Operations Research (GMOOR). This so- ciety which was founded in 1977 pursues the goal to support and facilitate research, development, application and education in an area where mathematics, economICS, operations research, computer science and system theory come together. th The 16 ' Symposium on Operations Research stood under t.he auspices of the Minister- priisident of the state of Rheinland-Pfalz, Rudolf Scharping. The opening addresses were given by the president of the Universitiit Trier, Professor Hasler, by the Minister fur Wissenschaft und Weiterbildung, Professor Zollner, and by Professor Hettich, on behalf of the organizers. These addresses are printed as part of the introductory material of this volume. The conference was attended by 351 participants from 29 countries; more than 70% of the participants gave lectures on their current res each interests, surveys on spe- cial topics or software demonstrations. They made the meeting truely a successful international forum for scientific exchange. The conference was highlighted by the award of the society's scientific prize in memo- riam Rudolf Henn to Professor R.E. Burkard, Technical University Graz, and his plenary GMOOR-Award winner lecture on Convexity and Discrete Optimization.