This is the eleventh book in the series the Common Core of European Private Law. This project was launched in 1993 at the University of Trento under the auspices of the late Professor Rudolf B. Schlesinger. The methodology used in the Trento project is novel. By making use of case studies it goes beyond mere description to detailed enquiry into how most European Union legal systems resolve specific legal questions in practice, and leads to thorough comparison between those systems. It is our hope that these volumes will provide scholars with a valuable tool for research in comparative law and in their own legal systems. The collection of materials that the Common Core project is offering to the scholarly community is already quite extensive and will become even more so when more volumes are published. The availability of materials attempting a genuine analysis of how things are is, in our opinion, a prerequisite for a stimulating and critical discussion on how they should be. Perhaps in the future European private law will be authoritatively restated or even codified, as is envisaged in the Draft Common Frame of Reference. The analytical work carried on by the nearly 300 scholars involved in the Common Core project is a precious asset of knowledge and legitimisation for any such normative enterprise.