Table 2. Network statistics of the co-authorship networks in the three samples (Scopus data).

Sample 1		Sample 2		Sample 3
Metric	Value	Metric	Value	Metric	Value
N° Nodes	7971	N° Nodes	5590	N° Nodes	2753
N° Edges	18689	N° Edges	12657	N° Edges	5309
Density	0.0006	Density	0.0008	Density	0.001
Diameter	14	Diameter	12	Diameter	8
N° Clusters	1910	N° Clusters	1378	N° Clusters	790
Cluster size (avg)	4.1	Cluster size (avg)	4.1	Cluster size (avg)	3.5
Cluster size (std)	5.8	Cluster size (std)	4.6	Cluster size (std)	3.0