Table 3.

Categorization of SMIs and relative indicators.

Indicator	Description	Category of SMI
Hub Index	Social media users are sorted on the basis of the total number of messages sent to important users.	Writer
Authority Index	Social media users are sorted on the basis of the number of messages received from the most active users.	Authority
Centrality Index	Social media users are sorted on the basis of a k-shell decomposition analysis (considering the number of citations and connections)	Spreader