“…To quantify the participation of different authors, many research works calculate the number of authors [e.g. (Abramo et al, 2009;Abrizah et al, 2012;Al et al, 2006;Glanzel, 2002;Hirsch, 2010;Zhou et al, 2007), etc.]. Also frequent number of research centers (Bordons & Barrigon, 1992;Montoya et al, 2014;Rojas-Sola & Jorda-Albinana, 2009a;Rojas-Sola & San-Antonio-Gomez, 2010b;Rosas et al, 2011;Voracek & Loibl, 2009) and / or number of countries participating in each article (Chen et al, 2007;Katz & Hicks, 1997;Keiser & Utzinger, 2005;Uzun, 2004).…”