This book is the result of my research perfonned at the University Kiel under the supervision of Professor Dr. Andreas Drexl. I am very grateful to him for suggesting the subject as well as for his guidance and support during the preparation. Professor Dr. Klaus Brockhoff deserves thanks for under- taking the task of the secondary assessment. The Institut fur Betriebswirtschaftslehre in Kiel and especially my col- leagues Dr. Knut Haase, Carsten Jordan, AlfKimrns, and Dr. Frank Salewski provided a stimulating environment. Particularly, I am indebted to Dr. Arno Sprecher and Andreas Schinner. The results of Chapter 2 and 3, respectively, are outcome of joint research with Arno; Andreas proof-read the entire manuscript. Furthennore, I would like to express my gratitude to Prof. Dr. Erik Demeulemeester, Prof Dr. James H. Patterson, Prof Dr. Roman Slowinski, and Prof Dr. Ramon Alvarez-Valdes for the valuable help they provided with suggestions, papers, and computer programs. I, As to the technical realisation of this book, lowe thanks to Reimer Karlsen for coding and impl menting parts of the algorithms, to Marc Schumann for drawing all figures, to Ina Kantowski who looked after the literature, and to Uwe Penke for providing a ready-to-use computer-laboratory. The gratitude that I feel towards my family requires no further comments.