This paper is written as a stretchtext, which means that it will be longer or shorter at your wish. It is divided in four chapters, and each chapter has a few sentences of the abstract as an introduction. Each chapter consists of two to four pages, and these pages may be shorter or longer as you "stretch" to include additional paragraphs or "collapse" to leave paragraphs out.
To read the abstract, read just the chapter introductions in sequence. If you read all the pages in each chapter without stretching them, you are reading a "short paper." If you stretch out all the pages fully, you read a "full paper." You are of course free to choose any length between these points.
The stretching function requires a modern browser with JavaScript enabled. Popup window blocking should be off for best effect.
To be specific, your browser needs to support the Document Object Model (DOM), and Cascading Style Sheets (CSS) level 1. Test your browser by clicking the "collapse" link below. If this paragraph doesn't disappear, you need to turn on JavaScript, or get a more recent browser, like the ones recommended by Browse happy.
I would like to thank my wonderful research assistant Ragnhild Fjellro for her assistance with this work