In presenting this book I would like to sincerely thank everyone who in different ways has been helpful and contributed to its realization.

I give special thanks to: Espen M. Andersen, Stewart Clark, Houchang Fathi, Tone Gengenbach, Monica Gustad, Kjetil Hoel, Arthur Holmen, Katrine Jakobsen, Vidar Knutsen, Inger Kolseth, Christian Norberg-Schultz, Tormod Raen, Jorun Schanke Olsen, Bodvar Schjelderup, J&uumlrgen Spelda, Sidsel Sturt, Michal Tomaszewicz, Arno Vigmostad, Erik Wiggen, Bernard Witte, Berit &Oslashstberg and Nils &Oslashstlund.

And I thank the students who through the two periods (1958-70, 1985-95) have worked with me in the laboratories. It has been a pleasure to be in an atmosphere of interest and enthusiasm, and to experience all the various ideas.

A well known sentence has been repeatedly confirmed: "To teach is to learn".

I also want to express my gratitude to the Research Council of Norway for financial support in printing the book.

Mogul Media and William Klippgen have been responsible for the World Wide Web publishing.

Trondheim 1995, Liv Arvesen