1. Science Policy and Strategy Department, Administrative Headquarters of the Max Planck Society, Hofgartenstr. 8, 80539 Munich, Germany
2. Centre for R&D Monitoring, Faculty of Social Sciences, University of Antwerp, Middelheimlaan 1, 2020 Antwerpen, Belgium
3. Statistical Cybermetrics Research Group, School of Mathematics and Computer Science, University of Wolverhampton Wulfruna Street, Wolverhampton WV1 1LY, UK
4. School of Information Studies, University of Wisconsin—Milwaukee, P.O. Box 413, Milwaukee, WI, USA, 53201