This book is based on research conducted for the purpose of a Ph.D. thesis. Therefore I would like to express my most sincere gratitude to all my supervisors during these years, Ms. Elizabeth Kirk, Dr. Jacques Hartmann, Prof. Fiona Raitt and Dr. Padraig McAuliffe, under whose enthusiastic supervision the research was completed. Their support throughout this study was unlimited, and without their help this book would have been impossible to complete. I would also like to express my gratitude to Asser/Springer for showing confidence in my work and for their help throughout the process of publishing. I thank colleagues and friends from the University of Dundee in the UK for reading and commenting on several chapters of this book. I would like to acknowledge with gratitude the love of my family and friends in Greece who gave me endless moral support over the past years. Last but not least, I would like to express my honest gratitude to Manos Primikyrios, for his endless encouragement and patience and for his constant love and support when they were most required.