1. ADAPT Centre, School of Computer Science and Statistics, Trinity College Dublin, Ireland. E-mail: debattij@tcd.ie
2. Fraunhofer IAIS, Schloss Birlinghoven, 53754 Sankt Augustin, Germany. E-mail: langec@iai.uni-bonn.de
3. TIB Leibniz Information Centre for Science and Technology & Leibniz University of Hannover, Am Welfengarten 1b, 30167 Hannover, Germany. E-mail: auer@l3s.de
4. Faculty of Economics, Management and Accountancy, University of Malta, Msida MSD 2080, Malta. E-mail: dominic.cortis@um.edu.mt