This article is dedicated to my daughters Íria and Noa, to my wife Luz, and to my mother, M. Teresa. I also thank Dr. Ángel Amado Calvo, who read the early drafts and gave me his valuable and well-informed opinion. Likewise, I am gra- teful to Professor Paloma Fernández Pérez, who, while co-directing my thesis, tried to guide me along the paths of true academic ri- gor. Finally, to Professor José Luis García Ruiz, who always offered me his invaluable support in the articles I published after the thesis.