Table 2.

Main information about the collection reported separately for “earlier analysis” (EA: 1993–2005) and “recent analysis” (RA: 2006–2018), with EA-RA variation

Main information about collection
Period	EA (1993–2005)	RA (2006–2018)	EA-RA variation
Documents	218	1307	5.00
Sources	34	85	1.50
Keywords plus (ID)	493	2557	4.19
Author’s keywords (DE)	368	2462	5.69
Average citations per documents	62	15	− 0.76
Authors	397	2666	5.72
Author appearances	722	5393	6.47
Authors of single-authored documents	26	37	0.42
Authors of multi-authored documents	371	2692	6.26
Single-authored documents	34	46	0.35
Documents per Author	0.549	0.490	− 0.11
Authors per document	1.82	2	0.12
Co-Authors per documents	3.31	4	0.25
Collaboration Index	2.02	2	0.03