1. Robert Tijssen (corresponding author), DST-NRF Centre of Excellence in Scientometrics and Science, Technology, Innovation Policy (SciSTIP), University of Stellenbosch, Stellenbosch, South Africa; Centre for Science and Technology Studies (CWTS), Leiden University, Leiden, Netherlands.
2. Jos Winnink, Centre for Science and Technology Studies (CWTS), Leiden University, Leiden, Netherlands.