In the next paragraphs, the use of references will be restricted to the research studies of the OR&S group, and only when no results in our OR&S group are available will I mention other references from literature. Needless to say, all of our research work cited in the next paragraphs is based on the excellent work of other researchers. I have chosen not to mention the enormous list of references to papers and books that I have used as a background or source of inspiration for my own research for two reasons. The first, and most obvious, reason is that the list of references would simply be too long, and the risk that I should forget an important reference is not worth taking. A second, and what I believe to be a very pragmatic, reason is that most, if not all, of the references can be found in my own work (books, papers, websites) that I have mentioned here. However, by not mentioning other sources from literature, I by no means wish to give the impression that these external references and their authors are less important. On the contrary—these authors have been crucial in formulating my own research ideas and hypotheses, and they have played an essential role in my reviewing and updating my own work. They have been my main inspiration and the driver for gradually defining my own research track—and without them, there would be no me.