Presentation at the international conference "Web Archives as Scholarly Sources: Issues, Practices and Perspectives". RESAW conference, 8-10 June 2015. Incuba Science Park, Aabogade, Aarhus. Organised by RESAW, Aarhus University, the State and University Library (Denmark), the Royal Library (Denmark), l’Institut des sciences de la communication du CNRS, Université de Lille 3, the Institute of Historical Research (University of London), the University of Amsterdam, the British Library, and Leibniz University Hannover/ALEXANDRIA.