“…They are the main tool used to diffuse knowledge and to enable the process of scientific progress (Braun, 2004). Consequently, despite some limitations (Jonkers, 2009), co-authorships can be considered "one of the most tangible and well documented forms of scientific collaboration" [Glänzel and Schubert, (2004), p.257] and are used in numerous studies analysing national and international research networks (Jonkers, 2009;Luukonen et al, 1993;Adams and Loach, 2015;Endenich and Trapp, 2015, to cite some). Such links tend not only to increase with time, but also to define stable and persistent networks among researchers and countries (Acedo et al, 2006;Uddin et al, 2012).…”