The medieval capbreus, property files, the Registry of Mortgages and the Land Registry are important sources for the study of shapes, conditions and structures of land ownership in the various eras that were in force. Their study can help understand the characteristics of a society in any historical era. But to make more comprehensible the main objective of this book, it is necessary to highlight yet another aspect to these sources. To be alive, that is useful, they should collect and gather information about the contemporary state, movements, changes and quality of property rights. Therefore, these sources are not only important historical databases, which means that not only provide objective historical data useful to the historian on an important issue, but are in themselves historical systems of information, often complex and Often biased, always influenced by the legal framework, but also for everyday social relations.