Arrow Plus builds on and further implements the Arrow system, developed within the Arrow project (eContent Plus programme). Arrow is a system to facilitate libraries and other users in their diligent search for rightholders in works that are to be included in a digitisation programme of books, through querying a network of European data sources. Arrow Plus plans to extend the number of countries covered, delivering a genuinely pan-European infrastructure, closing the gap in book data quality between European countries. Arrow Plus will also analyse the extension of Arrow services to the image domain.Interoperability of European book data sources, between countries and between domains - library catalogues, Books in Print (BIP) databases and Reproduction Rights Organisations (RRO) repertoire - is the primary deliverable of the project. Particular attention is paid to the establishment of new book data sources, including BIP and RROs repertoire databases, where these sources do not exist, so to allow a larger number of countries to be covered by the Arrow service.A new technical infrastructure to establish a BIP service in the countries where none exists will represent one direct outcome of the project, as well as the built-in ARROW compliance for the IFRRO Standard software for RROs.The Arrow Plus consortium includes representatives of all relevant stakeholders: libraries, publishers, creators (both writers and visual artists), RROs, photo agencies, and book standards organisations. All are represented at the highest possible level, by the respective European or international organisations in addition to a number of national representatives. Users (libraries, in particular) and data providers (libraries, BIPs and RROs) are also closely involved in the project.