Determining the authorship and originality of artistic works is essential for fully enjoying art, and for the correct functioning of the market and many cultural centres. It is one of the tasks falling not only to institutions but also to artists' foundations, museums, public administrations, academics, gallery owners and art collectors. All those involved with this part of the artistic world encounter problems. This book, derived from an international seminar organised by the Gala-Salvador Dalí Foundation shares the knowledge, experience and opinions of some of the most prestigious experts on these subjects. Furthermore, it provides some new angles, proposals and linguistic elements that can help to understand the difficulties presented by the topic and to improve its legal regulation.